Treatment Preferences for Cardiac Procedures of Patients With Chronic Kidney Disease in Acute Coronary Syndrome: Design and Pilot Testing of a Discrete Choice Experiment.

BACKGROUND: Chronic kidney disease is associated with a high incidence of acute coronary syndrome and related morbidity and mortality. Treatment choices for patients with chronic kidney disease involve trade-offs in the potential benefits and harms of invasive management options. OBJECTIVE: The objective was to quantify preferences of patients with chronic kidney disease toward invasive heart procedures. DESIGN: Design and pilot a discrete choice experiment. SETTING: We piloted the discrete choice experiment in 2 multidisciplinary chronic kidney disease clinics in Calgary, Alberta, using an 8-question survey. PATIENTS: Eligible patients included those aged 18 years and older, an estimated glomerular filtration rate < 45 mL/min/1.73 m2, not currently receiving dialysis, and able to communicate in English. MEASUREMENTS: Quantification of the average importances of key attributes of invasive heart procedures. METHODS: We identified attributes most important to patients and physicians concerning invasive versus conservative management for acute coronary syndrome, using semi-structured qualitative interviews. Levels for each attribute were derived from analysis of early invasive versus conservative acute coronary syndrome management clinical trials and cohort studies, where subgroups of patients with chronic kidney disease were reported. We designed the pilot study with patient partners with relevant lived experience and considered statistical efficiency to estimate main effects and interactions, as well as response efficiency. Hierarchical Bayesian estimation was used to quantify average importances of attributes. RESULTS: We recruited 43 patients with chronic kidney disease, mean (SD) age 67 (14) years, 67% male, and 35% with a history of cardiovascular disease, of whom 39 completed the survey within 2 weeks of enrollment. The results of the pilot revealed acute kidney injury requiring dialysis and permanent kidney replacement therapy, as well as death within 1 year were the most important attributes. Measures of internal validity for the pilot discrete choice experiment were comparable to those for other published discrete choice experiments. LIMITATIONS: Discrete choice experiments are complex instruments and often cognitively demanding for patients. This survey included multiple risk attributes which may have been challenging for some patients to understand. CONCLUSIONS: This pilot study demonstrates the feasibility of a discrete choice experiment to quantify preferences of patients with chronic kidney disease toward the benefits and trade-offs related to invasive versus conservative management for acute coronary syndrome. These preliminary findings suggest that patients with chronic kidney disease may be on average similarly risk averse toward kidney replacement therapy and death. This pilot information will be used to inform a larger discrete choice experiment that will refine these estimates of patient preferences and characterize subgroups with distinct treatment preferences, which should provide new knowledge that can facilitate shared decision-making between patients with chronic kidney disease and their care providers in the setting of acute coronary syndrome.

CONTEXTE: L'insuffisance rénale chronique (IRC) est associée à une forte incidence du syndrome coronarien aigu, de même qu'à la morbidité et à la mortalité qui y sont liées. Les options de traitement pour les patients atteints d'IRC impliquent de faire des compromis sur les avantages et inconvénients des options invasives. OBJECTIF: Quantifier les préférences des patients atteints d'IRC quant aux procédures cardiaques invasives. CONCEPTION: Concevoir et piloter une expérience avec choix discrets. CADRE: Nous avons mené cette expérience avec choix discrets dans deux cliniques multidisciplinaires de néphropathie chronique de Calgary (Alberta) à l'aide d'un sondage en huit questions. SUJETS: Les patients admissibles étaient des adultes avec un débit de filtration glomérulaire estimé (DFGe) inférieur à 45 mL/min/1,73 m 2 et ne suivant pas de traitements de dialyse. Les patients inclus devaient être capables de communiquer en anglais. MESURES: Quantification de l'importance moyenne des principaux attributs des procédures cardiaques effractives. MÉTHODOLOGIE: Les attributs les plus importants pour les patients et les médecins concernant une gestion invasive par rapport à une gestion conservatrice du syndrome coronarien aigu ont été déterminés à l'aide d'interviews qualitatives semi-structurées. L'analyse d'essais cliniques et d'études de cohorte ayant inclus des sous-groupes de patients atteints d'IRC et portant sur la gestion invasive précoce du syndrome coronarien aigu par opposition à une gestion conservatrice a permis de dériver les le degré d'importance pour chaque attribut. Nous avons conçu l'étude pilote en compagnie de patients partenaires ayant une expérience vécue pertinente et nous avons tenu compte de l'efficacité statistique pour estimer les principaux effets et interactions, de même que l'efficacité de la réponse. Une estimation hiérarchique bayésienne a été employée pour quantifier l'importance moyenne des attributs. RÉSULTATS: Nous avons recruté 43 patients atteints d'IRC dont l'âge moyen (É-T) était de 67 ans (14). La cohorte était constituée à 67 % d'hommes et 35 % des sujets avaient des antécédents de maladies cardiovasculaires. L'étude porte sur les 39 patients ayant rempli le questionnaire dans les deux semaines suivant le recrutement. Les résultats de l'étude pilote ont révélé que la mortalité dans la première année et l'insuffisance rénale aiguë (IRA) nécessitant la dialyse et une thérapie de remplacement rénal permanente étaient les attributs les plus importants. Les mesures des intervalles de validité de cette expérience pilote avec choix discrets étaient similaires à ceux des autres expériences publiées du même type. LIMITES: Les expériences avec choix discrets sont des outils complexes et souvent exigeants pour les patients sur le plan cognitif. Ce questionnaire comportait plusieurs attributs de risque qui ont peut-être été difficiles à comprendre pour certains patients. CONCLUSION: Cette étude pilote démontre la faisabilité d'une expérience avec choix discrets pour qualifier les préférences des patients atteints d'IRC en ce qui concerne les avantages et les compromis liés à une gestion invasive ou conservatrice du syndrome coronarien aigu. Ces résultats préliminaires semblent indiquer que les patients atteints d'IRC seraient en moyenne tout aussi réticents envers le risque de thérapie de remplacement rénal qu'envers le risque de décès. Les informations tirées de ce pilote serviront à orienter une plus vaste expérience avec choix discrets qui raffinera ces estimations des préférences des patients et caractérisera les sous-groupes ayant des préférences de traitements distinctes. Ceci fournira de nouvelles connaissances susceptibles de faciliter la prise de décision partagée entre les patients atteints d'IRC et leurs fournisseurs de soins dans le contexte du syndrome coronarien aigu.

Health Assessment Questionnaire at One Year Predicts All-Cause Mortality in Patients With Early Rheumatoid Arthritis.

OBJECTIVE: Higher self-reported disability (high Health Assessment Questionnaire [HAQ] score) has been associated with hospitalizations and mortality in established rheumatoid arthritis (RA), but associations in early RA are unknown. METHODS: Patients with early RA (symptom duration <1 year) enrolled in the Canadian Early Arthritis Cohort who initiated disease-modifying antirheumatic drugs and had completed HAQ data at baseline and 1 year were included in the study. Discrete-time proportional hazards models were used to estimate crude and multi-adjusted associations of baseline HAQ and HAQ at 1 year with all-cause mortality in each year of follow-up. RESULTS: A total of 1,724 patients with early RA were included. The mean age was 55 years, and 72% were women. Over 10 years, 62 deaths (3.6%) were recorded. Deceased patients had higher HAQ scores at baseline (mean ± SD 1.2 ± 0.7) and at 1 year (0.9 ± 0.7) than living patients (1.0 ± 0.7 and 0.5 ± 0.6, respectively; P < 0.001). Disease Activity Score in 28 joints (DAS28) was higher in deceased versus living patients at baseline (mean ± SD 5.4 ± 1.3 versus 4.9 ± 1.4) and at 1 year (mean ± SD 3.6 ± 1.4 versus 2.8 ± 1.4) (P < 0.001). Older age, male sex, lower education level, smoking, more comorbidities, higher baseline DAS28, and glucocorticoid use were associated with mortality. Contrary to HAQ score at baseline, the association between all-cause mortality and HAQ score at 1 year remained significant even after adjustment for confounders. For baseline HAQ score, the unadjusted hazard ratio (HR) was 1.46 (95% confidence interval [95% CI] 1.02-2.09), and the adjusted HR was 1.25 (95% CI 0.81-1.94). For HAQ score at 1 year, the unadjusted HR was 2.58 (95% CI 1.78-3.72), and the adjusted HR was 1.75 (95% CI 1.10-2.77). CONCLUSION: Our findings indicate that higher HAQ score and DAS28 at 1 year are significantly associated with all-cause mortality in a large early RA cohort.

Palindromic Rheumatism Frequently Precedes Early Rheumatoid Arthritis: Results From an Incident Cohort.

BACKGROUND: This multicenter incident cohort aimed to characterize how often early rheumatoid arthritis (ERA) patients self-report episodic joint inflammation (palindromic rheumatism) preceding ERA diagnosis and which characteristics differentiate these patients from those without prior episodic symptoms. METHODS: Data were from patients with early confirmed or suspected RA (more than 6 weeks and less than 12 months) enrolled in the Canadian Early ArThritis CoHort (CATCH) between April 2017 to March 2018 who completed study case report forms assessing joint pain and swelling prior to ERA diagnosis. Chi-square and t tests were used to compare characteristics of patients with and without self-reported episodic joint inflammation prior to ERA diagnosis. Multivariable logistic regression was used to identify sociodemographic and clinical measures associated with past episodic joint inflammation around the time of ERA diagnosis. RESULTS: A total of 154 ERA patients were included; 66% were female, and mean (SD) age and RA symptom duration were 54 (15) years and 141 (118) days. Sixty-five (42%) ERA patients reported a history of episodic joint pain and swelling, half of whom reported that these symptoms preceded ERA diagnosis by over 6 months. ERA patients with past episodic joint inflammation were more often female, had higher income, were seropositive, had more comorbidities, fewer swollen joints, and lower Clinical Disease Activity Index (CDAI) around the time of ERA diagnosis (P < 0.05). These associations remained significant in multivariable regression adjusting for other sociodemographic and RA clinical measures. CONCLUSION: Almost half of ERA patients experienced episodic joint inflammation prior to ERA diagnosis. These patients were more often female, had higher income, and presented with milder disease activity at ERA diagnosis.

Prevalence and Characteristics of Metabolic Syndrome Differ in Men and Women with Early Rheumatoid Arthritis.

Objective: Metabolic syndrome (MetS) prevalence in early rheumatoid arthritis (ERA) is conflicting. The impact of sex, including menopause, has not been described. We estimated the prevalence and factors associated with MetS in men and women with ERA. Methods: A cross-sectional study of the Canadian Early Arthritis Cohort (CATCH) was performed. Participants with baseline data to estimate key MetS components were included. Sex-stratified logistic regression identified baseline variables associated with MetS. Results: The sample included 1543 participants; 71% were female and the mean age was 54 (SD 15) years. MetS prevalence was higher in men 188 (42%) than women 288 (26%, P < 0.0001) and increased with age. Frequent MetS components in men were hypertension (62%), impaired glucose tolerance (IGT, 40%), obesity (36%), and low high-density lipoprotein cholesterol (36%). Postmenopausal women had greater frequency of hypertension (65%), IGT (32%), and high triglycerides (21%) compared with premenopausal women (P < 0.001). In multivariate analysis, MetS was negatively associated with seropositivity and pulmonary disease in men. Increasing age was associated with MetS in women. In postmenopausal women, corticosteroid use was associated with MetS. Psychiatric comorbidity was associated with MetS in premenopausal women. MetS status was not explained by disease activity or core RA measures. Conclusion: The characteristics and associations of MetS differed in men and women with ERA. Sex differences, including postmenopausal status, should be considered in comorbidity screening. With this knowledge, the interplay of MetS, sex, and RA therapeutic response on cardiovascular outcomes should be investigated.

Effect of footbath protocols for prevention and treatment of digital dermatitis in dairy cattle: A systematic review and network meta-analysis.

Digital dermatitis (DD) is an infectious bacterial disease affecting cattle feet. Footbaths are a common herd-level control method for DD; however, variations in product, concentration, and frequency of use complicate comparisons between protocols. The objective of this systematic review was to evaluate all walk-through footbath protocols reported that determined efficacy for prevention and treatment of DD lesions in dairy cattle. An extensive literature search was conducted, including electronic databases and gray literature updated until March 2018. Studies identified included all liquid walk-through footbath protocols that were compared to other footbath protocols or no footbath. Only studies with treatment or prevention of DD lesions as an outcome were included. Literature search and subsequent screening identified 14 publications with 24 treatment comparisons and 24 prevention comparisons. Studies included mostly had low and/or unclear risks of bias. Descriptive analyses were performed according to prevention and treatment outcomes, with case and success definitions summarized as odds ratios (OR). A subsequent network meta-analysis was conducted of 11 studies, comparing 17 protocol comparisons for the prevention outcome and 10 studies comparing 19 protocol comparisons for the treatment outcome, using semi-informative priors in a Bayesian statistical framework. Results of a random effects Bayesian network meta-analysis indicated only 5% copper sulfate used at least 4 times/wk was superior to both no footbath (OR: 5.26; 95% CrI: 1.27-28.8) and a water placebo (OR: 9.47; 95% CrI: 1.03-85.8) in treatment of DD. No other protocol was associated with a reduction in DD, and there were no differences in pair-wise comparisons between any active treatments. Unfortunately, for both outcomes (treatment and prevention), small sample sizes (adjusted for clustering) limited the power to detect substantial differences between protocol effects. Thus, despite widespread use of footbaths, limited strength of evidence for use remains and standardized protocols with large sample sizes are needed to further investigate effectiveness of footbath protocols for control of DD. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Systematic review with meta-analysis: comparative efficacy of biologics for induction and maintenance of mucosal healing in Crohn's disease and ulcerative colitis controlled trials.

BACKGROUND: Mucosal healing is an important therapeutic endpoint in the management of Crohn's disease (CD) and ulcerative colitis (UC). Limited data exist regarding the comparative efficacy of various therapies in achieving this outcome. AIM: To perform a systematic review and meta-analysis of biologics for induction and maintenance of mucosal healing in Crohn's disease and ulcerative colitis. METHODS: We performed a systematic review and meta-analysis of randomised controlled trials (RCT) examining mucosal healing as an endpoint of immunosuppressives, anti-tumour necrosis factor α (anti-TNF) or anti-integrin monoclonal antibody therapy for moderate-to-severe CD or UC. Pooled effect sizes for induction and maintenance of mucosal healing were calculated and pairwise treatment comparisons evaluated using a Bayesian network meta-analysis. RESULTS: A total of 12 RCTs were included in the meta-analysis (CD - 2 induction, 4 maintenance; UC - 8 induction, 5 maintenance). Duration of follow-up was 6-12 weeks for induction and 32-54 weeks for maintenance trials. In CD, anti-TNFs were more effective than placebo for maintaining mucosal healing [28% vs. 1%, Odds ratio (OR) 19.71, 95% confidence interval (CI) 3.51-110.84]. In UC, anti-TNFs and anti-integrins were more effective than placebo for inducing (45% vs. 30%) and maintaining mucosal healing (33% vs. 18%). In network analysis, adalimumab therapy was inferior to infliximab [OR 0.45, 95% credible interval (CrI) 0.25-0.82] and combination infliximab-azathioprine (OR 0.32, 95% CrI 0.12-0.84) for inducing mucosal healing in UC. There was no statistically significant pairwise difference between vedolizumab and anti-TNF agents in UC. CONCLUSIONS: Anti-TNF and anti-integrin biological agents are effective in inducing mucosal healing in UC, with adalimumab being inferior to infliximab or combination therapy. Infliximab and adalimumab were similar in CD.

Systematic review with meta-analysis: comparative efficacy of immunosuppressants and biologics for reducing hospitalisation and surgery in Crohn's disease and ulcerative colitis.

INTRODUCTION: Crohn's disease (CD) and ulcerative colitis (UC) have a progressive course leading to hospitalisation and surgery. The ability of existing therapies to alter disease course is not clearly defined. AIM: To investigate the comparative efficacy of currently available inflammatory bowel disease (IBD) therapies to reduce hospitalisation and surgery. METHODS: We conducted a systematic review in MEDLINE/PubMed for randomised controlled trials (RCT) published between January 1980 and May 2016 examining efficacy of biological or immunomodulator therapy in IBD. We performed direct comparisons of pooled proportions of hospitalisation and surgery. Pair-wise comparisons using a random-effects Bayesian network meta-analysis were performed to assess comparative efficacy of different treatments. RESULTS: We identified seven randomised controlled trials (5 CD; 2 UC) comparing three biologics and one immunomodulator with placebo. In CD, anti-TNF biologics significantly reduced hospitalisation [Odds ratio (OR) 0.46, 95% confidence interval (CI) 0.36-0.60] and surgery (OR 0.23, 95% CI 0.13-0.42) compared to placebo. No statistically significant reduction was noted with azathioprine or vedolizumab. Azathioprine was inferior to both infliximab and adalimumab in preventing CD-related hospitalisation (>97.5% probability). Anti-TNF biologics significantly reduced hospitalisation (OR 0.48, 95% CI 0.29-0.80) and surgery (OR 0.67, 95% CI 0.46-0.97) in UC. There were no statistically significant differences in the pair-wise comparisons between active treatments. CONCLUSIONS: In CD and UC, anti-TNF biologics are efficacious in reducing the odds of hospitalisation by half and surgery by 33-77%. Azathioprine and vedolizumab were not associated with a similar improvement, but robust conclusions may be limited due to paucity of RCTs.

The major component of the cellulosomes of anaerobic fungi from the genus Piromyces is a family 48 glycoside hydrolase.

Sequencing of two cDNAs from the anaerobic fungi Piromyces equi and Piromyces sp. strain E2 revealed that they both encode a glycoside hydrolase (GH) family 48 cellulase, containing two C-terminal fungal dockerin domains. N-terminal sequencing of the major component of the Piromyces multi-enzyme cellulase/hemicellulase complex, termed the cellulosome, showed that these 80 kDa proteins corresponded to the GH family 48 enzyme. These data show for the first time that GH family 48 cellulases are not confined to bacteria, and that bacterial and fungal cellulosomes share the same pivotal component.

A novel carbohydrate-binding protein is a component of the plant cell wall-degrading complex of Piromyces equi.

The recycling of photosynthetically fixed carbon by the action of microbial plant cell wall hydrolases is a fundamental biological process that is integral to one of the major geochemical cycles and, in addition, has considerable industrial potential. Enzyme systems that attack the plant cell wall contain noncatalytic carbohydrate-binding modules (CBMs) that mediate attachment to this composite structure and play a pivotal role in maximizing the hydrolytic process. Anaerobic fungi that colonize herbivores are the most efficient plant cell wall degraders known, and this activity is vested in a high molecular weight complex that binds tightly to the plant cell wall. To investigate whether plant cell wall attachment is mediated by noncatalytic proteins, a cDNA library of the anaerobic fungus Piromyces equi was screened for sequences that encode noncatalytic proteins that are components of the cellulase-hemicellulase complex. A 1.6-kilobase cDNA was isolated encoding a protein of 479 amino acids with a M(r) of 52548 designated NCP1. The mature protein had a modular architecture comprising three copies of the noncatalytic dockerin module that targets anaerobic fungal proteins to the cellulase-hemicellulase complex. The two C-terminal modules of NCP1, CBM29-1 and CBM29-2, respectively, exhibit 33% sequence identity with each other but have no homologues in protein data bases. A truncated form of NCP1 comprising CBM29-1 and CBM29-2 (CBM29-1-2) and each of the two individual copies of CBM29 bind primarily to mannan, cellulose, and glucomannan, displaying the highest affinity for the latter polysaccharide. CBM29-1-2 exhibits 4-45-fold higher affinity than either CBM29-1 or CBM29-2 for the various ligands, indicating that the two modules, when covalently linked, act in synergy to bind to an array of different polysaccharides. This paper provides the first report of a CBM-containing protein from an anaerobic fungal cellulase-hemicellulase complex. The two CBMs constitute a novel CBM family designated CBM29 whose members exhibit unusually wide ligand specificity. We propose, therefore, that NCP1 plays a role in sequestering the fungal enzyme complex onto the plant cell wall.

Characterization of a cellulosome dockerin domain from the anaerobic fungus Piromyces equi.

The recycling of photosynthetically fixed carbon in plant cell walls is a key microbial process. In anaerobes, the degradation is carried out by a high molecular weight multifunctional complex termed the cellulosome. This consists of a number of independent enzyme components, each of which contains a conserved dockerin domain, which functions to bind the enzyme to a cohesin domain within the protein scaffoldin protein. Here we describe the first three-dimensional structure of a fungal dockerin, the N-terminal dockerin of Cel45A from the anaerobic fungus Piromyces equi. The structure contains a novel fold of 42 residues. The ligand binding site consists of residues Trp 35, Tyr 8 and Asp 23, which are conserved in all fungal dockerins. The binding site is on the opposite side of the N- and C-termini of the molecule, implying that tandem dockerin domains, seen in the majority of anaerobic fungal plant cell wall degrading enzymes, could present multiple simultaneous binding sites and, therefore, permit tailoring of binding to catalytic demands.

alpha-Galactosidase A from Pseudomonas fluorescens subsp. cellulosa: cloning, high level expression and its role in galactomannan hydrolysis.

A library of Pseudomonas fluorescens subsp. cellulosa genomic DNA, constructed in lambda ZAPII, was screened for alpha-D-galactosidase activity. The DNA inserts from six galactosidase-positive clones were rescued into plasmids. Restriction digestion and Southern analysis revealed that each of the plasmids contained a common DNA sequence. The sequence of the Pseudomonas DNA in one of the plasmids revealed a single open reading frame (aga27A) of 1215 bp encoding a protein of M(r) 45900, designated alpha-galactosidase 27A (Aga27A). Aga27A exhibited extensive sequence identity with alpha-galactosidases in glycoside hydrolase 27, and appeared to be a single domain protein. The recombinant alpha-galactosidase was expressed at high levels in Escherichia coli and the biophysical properties and substrate specificity of the enzyme were evaluated. The data showed that Aga27A was a mesophilic neutral acting non-specific alpha-galactosidase. Both P. fluorescens subsp. cellulosa mannanase A (ManA) and Aga27A hydrolyse the polymeric substrate, carob galactomannan. Sequential hydrolysis with AgaA followed by ManA, or ManA followed by AgaA enhanced product release. The positive effects of sequential hydrolysis are discussed.

A novel Cellvibrio mixtus family 10 xylanase that is both intracellular and expressed under non-inducing conditions.

Hydrolysis of the plant cell wall polysaccharides cellulose and xylan requires the synergistic interaction of a repertoire of extracellular enzymes. Recently, evidence has emerged that anaerobic bacteria can synthesize high levels of periplasmic xylanases which may be involved in the hydrolysis of small xylo-oligosaccharides absorbed by the micro-organism. Cellvibrio mixtus, a saprophytic aerobic soil bacterium that is highly active against plant cell wall polysaccharides, was shown to express internal xylanase activity when cultured on media containing xylan or glucose as sole carbon source. A genomic library of C. mixtus DNA, constructed in lambdaZAPII, was screened for xylanase activity. The nucleotide sequence of the genomic insert from a xylanase-positive clone that expressed intracellular xylanase activity in Escherichia coli revealed an ORF of 1137 bp (xynC), encoding a polypeptide with a deduced M(r) of 43413, defined as xylanase C (XylC). Probing a gene library of Pseudomonas fluorescens subsp. cellulosa with C. mixtus xynC identified a xynC homologue (designated xynG) encoding XylG; XylG and xynG were 67% and 63% identical to the corresponding C. mixtus sequences, respectively. Both XylC and XylG exhibit extensive sequence identity with family 10 xylanases, particularly with non-modular enzymes, and gene deletion studies on xynC supported the suggestion that they are single-domain xylanases. Purified recombinant XylC had an M(r) of 41000, and displayed biochemical properties typical of family 10 polysaccharidases. However, unlike previously characterized xylanases, XylC was particularly sensitive to proteolytic inactivation by pancreatic proteinases and was thermolabile. C. mixtus was grown to late-exponential phase in the presence of glucose or xylan and the cytoplasmic, periplasmic and cell envelope fractions were probed with anti-XylC antibodies. The results showed that XylC was absent from the culture media but was predominantly present in the periplasm of C. mixtus cells grown on glucose, xylan, CM-cellulose or Avicel. These data suggest that C. mixtus can express non-modular internal xylanases whose potential roles in the hydrolysis of plant cell wall components are discussed.

A comparison of enzyme-aided bleaching of softwood paper pulp using combinations of xylanase, mannanase and alpha-galactosidase.

Enzymatic pretreatment of softwood kraft pulp was investigated using xylanase A (XylA) from Neocallimastix patriciarum in combination with mannanase and alpha-galactosidase. Mannanase A (ManA) from Pseudomonas fluorescens subsp. cellulosa and ManA from Clostridium thermocellum, both family 26 glycosyl hydrolases, are structurally diverse and exhibit different pH and temperature optima. Although neither mannanase was effective in pretreating softwood pulp alone, both enzymes were able to enhance the production of reducing sugar and the reduction of single-stage bleached kappa number when used with the xylanase. Sequential incubations with XylA and P. fluorescens ManA produced the largest final kappa number reduction in comparison to control pretreated pulp. The release of galactose from softwood pulp by alpha-galactosidase A (AgaA) from P. fluorescens was enhanced by the presence of ManA from the same microorganism, and a single pretreatment with these enzymes, in combination with XylA. gave the most effective kappa number reduction using a single incubation. Results indicated that mixtures of hemicellulase activities can be chosen to enhance pulp bleachability.

A modular cinnamoyl ester hydrolase from the anaerobic fungus Piromyces equi acts synergistically with xylanase and is part of a multiprotein cellulose-binding cellulase-hemicellulase complex.

A collection of clones, isolated from a Piromyces equi cDNA expression library by immunoscreening with antibodies raised against affinity purified multienzyme fungal cellulase-hemicellulase complex, included one which expressed cinnamoyl ester hydrolase activity. The P. equi cinnamoyl ester hydrolase gene (estA) comprised an open reading frame of 1608 nt encoding a protein (EstA) of 536 amino acids and 55540 Da. EstA was modular in structure and comprised three distinct domains. The N-terminal domain was closely similar to a highly conserved non-catalytic 40-residue docking domain which is prevalent in cellulases and hemicellulases from three species of anaerobic fungi and binds to a putative scaffolding protein during assembly of the fungal cellulase complex. The second domain was also not required for esterase activity and appeared to be an atypically large linker comprising multiple tandem repeats of a 13-residue motif. The C-terminal 270 residues of EstA contained an esterase catalytic domain that exhibited overall homology with a small family of esterases, including acetylxylan esterase D (XYLD) from Pseudomonas fluorescens subsp. cellulosa and acetylxylan esterase from Aspergillus niger. This region also contained several smaller blocks of residues that displayed homology with domains tentatively identified as containing the essential catalytic residues of a larger group of serine hydrolases. A truncated variant of EstA, comprising the catalytic domain alone (EstA'), was expressed in Escherichia coli as a thioredoxin fusion protein and was purified to homogeneity. EstA' was active against synthetic and plant cell-wall-derived substrates, showed a marked preference for cleaving 1-->5 ester linkages between ferulic acid and arabinose in feruloylated arabino-xylo-oligosaccharides and was inhibited by the serine-specific protease inhibitor aminoethylbenzene-sulphonylfluoride. EstA' acted synergistically with xylanase to release more than 60% of the esterified ferulic acid from the arabinoxylan component of plant cell walls. Western analysis confirmed that EstA is produced by P. equi and is a component of the aggregated multienzyme cellulase-hemicellulase complex. Hybrid proteins, harbouring one, two or three iterations of the conserved 40-residue fungal docking domain fused to the reporter protein glutathione S-transferase, were produced. Western blot analysis of immobilized P. equi cellulase-hemicellulase complex demonstrated that each of the hybrid proteins bound to a 97 kDa polypeptide in the extracellular complex.

The type II and X cellulose-binding domains of Pseudomonas xylanase A potentiate catalytic activity against complex substrates by a common mechanism.

Xylanase A (Pf Xyn10A), in common with several other Pseudomonas fluorescens subsp. cellulosa polysaccharidases, consists of a Type II cellulose-binding domain (CBD), a catalytic domain (Pf Xyn10A(CD)) and an internal domain that exhibits homology to Type X CBDs. The Type X CBD of Pf Xyn10A, expressed as a discrete entity (CBD(X)) or fused to the catalytic domain (Pf Xyn10A'), bound to amorphous and bacterial microcrystalline cellulose with a K(a) of 2.5 x 10(5) M(-1). CBD(X) exhibited no affinity for soluble forms of cellulose or cello-oligosaccharides, suggesting that the domain interacts with multiple cellulose chains in the insoluble forms of the polysaccharide. Pf Xyn10A' was 2-3 times more active against cellulose-hemicellulose complexes than Pf Xyn10A(CD); however, Pf Xyn10A' and Pf Xyn10A(CD) exhibited the same activity against soluble substrates. CBD(X) did not disrupt the structure of plant-cell-wall material or bacterial microcrystalline cellulose, and did not potentiate Pf Xyn10A(CD) when not covalently linked to the enzyme. There was no substantial difference in the affinity of full-length Pf Xyn10A and the enzyme's Type II CBD for cellulose. The activity of Pf Xyn10A against cellulose-hemicellulose complexes was similar to that of Pf Xyn10A', and a derivative of Pf Xyn10A in which the Type II CBD is linked to the Pf Xyn10A(CD) via a serine-rich linker sequence [Bolam, Cireula, McQueen-Mason, Simpson, Williamson, Rixon, Boraston, Hazlewood and Gilbert (1998) Biochem J. 331, 775-781]. These data indicate that CBD(X) is functional in Pf Xyn10A and that no synergy, either in ligand binding or in the potentiation of catalysis, is evident between the Type II and X CBDs of the xylanase.

Homologous xylanases from Clostridium thermocellum: evidence for bi-functional activity, synergism between xylanase catalytic modules and the presence of xylan-binding domains in enzyme complexes.

Clostridium thermocellum produces a consortium of plant-cell-wall hydrolases that form a cell-bound multi-enzyme complex called the cellulosome. In the present study two similar xylanase genes, xynU and xynV, were cloned from C. thermocellum strain YS and sequenced. The deduced primary structures of both xylanases, xylanase U (XylU) and xylanase V (XylV), were homologous with the previously characterized xylanases from C. thermocellum strain F1. Truncated derivatives of XylV were produced and their biochemical properties were characterized. The xylanases were shown to be remarkably thermostable and resistant to proteolytic inactivation. The catalytic domains hydrolysed xylan by a typical endo-mode of action. The type VI cellulose-binding domain (CBD) homologue of XylV bound xylan and, to a smaller extent, Avicel and acid-swollen cellulose. Deletion of the CBD from XylV abolished the capacity of the enzymes to bind polysaccharides. The polysaccharide-binding domain was shown to have a key role in the hydrolysis of insoluble substrates by XylV. The C-terminal domain of XylV, which is absent from XylU, removed acetyl groups from acetylated xylan and acted in synergy with the glycosyl hydrolase catalytic domain of the enzyme to elicit the hydrolysis of acetylated xylan.

A family IIb xylan-binding domain has a similar secondary structure to a homologous family IIa cellulose-binding domain but different ligand specificity.

BACKGROUND: Many enzymes that digest polysaccharides contain separate polysaccharide-binding domains. Structures have been previously determined for a number of cellulose-binding domains (CBDs) from cellulases. RESULTS: The family IIb xylan-binding domain 1 (XBD1) from Cellulomonas fimi xylanase D is shown to bind xylan but not cellulose. Its structure is similar to that of the homologous family IIa CBD from C. fimi Cex, consisting of two four-stranded beta sheets that form a twisted 'beta sandwich'. The xylan-binding site is a groove made from two tryptophan residues that stack against the faces of the sugar rings, plus several hydrogen-bonding polar residues. CONCLUSIONS: The biggest difference between the family IIa and IIb domains is that in the former the solvent-exposed tryptophan sidechains are coplanar, whereas in the latter they are perpendicular, forming a twisted binding site. The binding sites are therefore complementary to the secondary structures of the ligands cellulose and xylan. XBD1 and CexCBD represent a striking example of two proteins that have high sequence similarity but a different function.

Bacterial xylanase expression in mammalian cells and transgenic mice.

The energy which simple-stomached livestock can derive from dietary plant material is limited by the lack of plant polysaccharide degrading enzymes in their gastro-intestinal (GI) tract and the inefficient microbial fermentation of such material in their hind-gut. In poultry the non-starch polysaccharides found in cereal grains can also impair normal digestive function as they form viscous gels in the GI tract inhibiting the breakdown and absorption of nutrients. The nutrition of such livestock could, therefore, be improved by the introduction of enzymes able to degrade plant polysaccharides in the small intestine. We describe the expression of a xylanase, XYLY', from the bacterium Clostridium thermocellum in mammalian cells and the exocrine pancreas of transgenic mice. The enzyme is synthesised, secreted and functionally active in the eukaryote system. This work demonstrates the feasibility of generating animals with the endogenous capacity to depolymerise the xylan component of hemi-cellulose.

Crystallization and preliminary X-ray analysis of arabinanase A from Pseudomonas fluorescens subspecies cellulosa.

Crystals of 1,5-alpha-arabinanase A from Pseudomonas fluorescens subspecies cellulosa have been obtained by vapour diffusion. The crystals belong to the space group P6122 with unit-cell parameters a = b = 91.6, c = 179.4 A with one molecule in the asymmetric unit. The native crystals and, to a much greater extent, heavy-atom soaked crystals are sensitive to radiation which necessitates cryocooling. Suitable cryocooling conditions have been established, though a shrinkage of the unit cell is observed, with a = b = 88.8 and c = 176.9 A.