Factors Influencing Liver Abnormalities in Psoriatic Arthritis Patients: A Comprehensive Study.

Objective: The aim of this study was to establish the incidence of liver abnormalities in psoriatic arthritis patients and identify the factors that contributed to this condition. Methods: This is a longitudinal cohort study. Psoriatic arthritis (PsA) patients with liver enzymes abnormalities were identified. Our control group consisted of PsA patient from the same cohort who had no history of liver abnormalities. Factors associated with liver abnormalities were identified using univariate and multivariate analysis. Results: A total of 247 of PsA patients were included and out of those, 99 developed liver enzymes abnormalities. The mean age of the patients was 56 years old (±13.5) with 56.1% female and 39.4% Indian descendants. The univariate logistic regression demonstrated that disease duration of PsA (OR=1.06, 95% CI=1.01 - 1.10, p=0.012), diabetes mellitus (OR=2.16, 95% CI=1.26 - 3.70, 0.005) and non-alcoholic fatty liver disease (NAFLD) (OR=3.90, 95% CI = 1.44 - 10.53, p=0.007) were associated with abnormal liver function in PsA patients. No association was found with both conventional synthetic disease-modifying antirheumatic drugs or biologics. Conclusion: Liver enzymes abnormalities in PsA patients were linked to disease duration, diabetes mellitus and NAFLD. For these high-risk populations, vigilant monitoring of liver function tests is vital for early detection and intervention.

A hierarchical cluster analysis for clinical profiling of tofacitinib treatment response in patients with rheumatoid arthritis.

Tofacitinib is the first oral JAK inhibitor approved for treating rheumatoid arthritis (RA). To enhance our understanding of tofacitinib drug response, we used hierarchical clustering to analyse the profiles of patient who responded to the treatment in a real-world setting. Patients who commenced on tofacitinib treatment were selected from 12 major rheumatology centres in Malaysia. The aim was to assess their response to tofacitinib defined as achieving DAS28-CRP/ESR ≤ 3.2 and DAS28 improvement > 1.2 at 12 weeks. A hierarchical clustering analysis was performed using sociodemographic and clinical parameters at baseline. All 163 RA patients were divided into three clusters (Clusters 1, 2 and 3) based on specific clinical factors at baseline including bone erosion, antibody positivity, disease activity and anaemia status. Cluster 1 consisted of RA patients without bone erosion, antibody negative, low baseline disease activity measure and absence of anaemia. Cluster 2 comprised of patients without bone erosion, RF positivity, anti-CCP negativity, moderate to high baseline disease activity score and absence of anaemia. Cluster 3 patients had bone erosion, antibody positivity, high baseline disease activity and anaemia. The response rates to tofacitinib varied among the clusters: Cluster 1 had a 79% response rate, Cluster 2 had a 66% response rate, and Cluster 3 had a 36% response rate. The differences in response rates between the three clusters were found to be statistically significant. This cluster analysis study indicates that patients who are seronegative and have low disease activity, absence of bone erosion and no signs of anaemia may have a higher likelihood of benefiting from tofacitinib therapy. By identifying clinical profiles that respond to tofacitinib treatment, we can improve treatment stratification yielding significant benefits and better health outcomes for individuals with RA.

Cardiomyopathy following COVID-19 vaccination in a patient with systemic lupus erythematosus.

There are an increasing number of reports of myocarditis associated with mRNA-based COVID-19 vaccination. We describe the case of a female patient with underlying systemic lupus erythematosus, who developed heart failure symptoms following a second dose of the BNT162b2 vaccine. Despite her history of refractory systemic lupus erythematosus, the disease remained stable after she began rituximab treatment. She underwent serial transthoracic echocardiogram and cardiac magnetic resonance imaging for the evaluation of cardiomyopathy. She showed improvement in cardiac function after treatment with glucocorticoids and intravenous immunoglobulin therapy.

Multifocal osteoarticular tuberculosis in a systemic lupus erythematosus (SLE) patient: a rarity or an underdiagnosed condition?

Tuberculosis (TB) and its association with rheumatic diseases have been widely recognised. Occurrence of multifocal skeletal involvement constitutes <5% of all skeletal TB cases. We present a Malay patient with multifocal osteoarticular TB (OATB). A 35 year-old SLE woman with background usage of corticosteroid therapy and Azathioprine presented with lupus nephritis flare. Renal biopsy revealed diffuse proliferative lupus nephritis and intravenous (IV) Cyclophosphamide 0.5 g/m2 (850 mg) was initiated. One week later, patient complained dorsum of left hand and right knee swelling. On physical examination, patient was afebrile and the left hand swelling was cystic in consistency while right knee was warm and tender. Erythrocyte Sedimentation Rate (ESR) was 50 mm/hr and C-Reactive Protein (CRP) was 9.4 mg/L. Her Mantoux test was positive with 20 mm induration. Wrist radiograph and chest radiograph was normal. Musculoskeletal ultrasound showed 4th extensor compartment tenosynovitis with Doppler signal and right knee effusion with synovial proliferation. Extensor tenosynovectomy and right knee aspiration was performed. Left hand excised tissue and right knee synovial fluid for acid-fast bacilli (AFB) stain, TB PCR, bacterial and fungal cultures were negative. Urgent histopathological examination of the excised tissue showed necrotising granulomatous inflammation. Patient was empirically started on TB treatment and subsequent mycobacterial culture confirmed the diagnosis of TB. The joints swelling resolved after one month of TB treatment. Multifocal OATB is an infrequent form of extrapulmonary TB and diagnosing OATB requires high index of suspicion particularly in SLE patient on immunosuppression. Prompt investigations are essential to the diagnosis of this rare condition for early initiation of anti-tuberculous therapy.

Tamponade by an expanding left ventricular pseudoaneurysm: A unique presentation.

Left ventricular free wall rupture secondary to myocardial infarction is an uncommon but catastrophic event requiring emergency surgery. We describe a unique presentation of left ventricular free wall rupture as delayed tamponade caused by a gradually expanding pseudoaneurysm compressing the left atrium, leading to pulmonary congestion that required increasing respiratory support to maintain oxygenation, and necessitated emergency surgery. We discuss the options available to treat pseudoaneurysms due to left ventricular free wall rupture.

Infarto agudo do miocárdio como apresentação inicial de granulomatose eosinofílica com poliangiite (anteriormente, síndrome de Churg Strauss) / Acute myocardial infarction as Eosinophilic granulomatosis with polyangiitis (formerly Churg Strauss syndrome) initial presentation

A granulomatose eosinofílica com poliangiite é uma vasculite primária rara, caracterizada por hipereosinofilia, asma de surgimento tardio e granulomas eosinofílicos extravasculares. Relatamos um caso apresentado inicialmente com infarto do miocárdio e que, ulteriormente, teve prosseguimento apenas com asma, manifestações cutâneas e neuropatia periférica. Os parâmetros laboratoriais revelaram hipereosinofilia com um padrão perinuclear negativo de autoanticorpos citoplásmicos antineutrófilos (p-ANCA). A biópsia de pele demonstrou vasculite leucocitoclástica com infiltração eosinofílica, diante de uma angiografia coronária normal. Os sintomas do paciente melhoraram com metilprednisolona IV, pulsoterapia com ciclofosfamida e azatioprina.

Eosinophilic granulomatosis with polyangiitis is a rare primary vasculitic disease characterized by hypereosinophilia, late onset asthma and extravascular eosinophil granulomas. We report a case presented initially with acute myocardial infarction which later only proceed with asthma, skin manifestations and peripheral neuropathy. Laboratory parameters showed hypereosinohpilia with negative perinuclear pattern of antineutrophil cytoplasmic autoantibodies (p-ANCA). Skin biopsy showed leucocytoclastic vasculitis with eosinophilic infiltration while coronary angiography was normal. The patient's symptoms improved with IV methylprednisolone, pulse cyclophosphamide and azathioprine.

[Acute myocardial infarction as Eosinophilic granulomatosis with polyangiitis (formerly Churg Strauss syndrome) initial presentation]. / Infarto agudo do miocárdio como apresentação inicial de granulomatose eosinofílica com poliangiite (anteriormente, síndrome de Churg Strauss).

Eosinophilic granulomatosis with polyangiitis is a rare primary vasculitic disease characterized by hypereosinophilia, late onset asthma and extravascular eosinophil granulomas. We report a case presented initially with acute myocardial infarction which later only proceed with asthma, skin manifestations and peripheral neuropathy. Laboratory parameters showed hypereosinohpilia with negative perinuclear pattern of antineutrophil cytoplasmic autoantibodies (p-ANCA). Skin biopsy showed leucocytoclastic vasculitis with eosinophilic infiltration while coronary angiography was normal. The patient's symptoms improved with IV methylprednisolone, pulse cyclophosphamide and azathioprine.

Patient's Knowledge and Perception Towards the use of Non-steroidal Anti-Inflammatory Drugs in Rheumatology Clinic Northern Malaysia.

OBJECTIVE: In Rheumatology, non-steroidal anti-inflammatory drugs (NSAIDs) has been widely prescribed and used. However, despite their clinical benefits in the management of inflammatory and degenerative joint disease, NSAIDs have considerable side effects, mostly affecting the upper gastrointestinal system, which therefore, limit their use. This study was conducted to determine the patients' knowledge and perception regarding the used of NSAIDS. METHODS: A total of 120 patients who attended the rheumatology clinic Hospital, Raja Permaisuri Bainun, Malaysia, and received NSAIDs more than 3 months were interviewed irrespective of their rheumatological conditions. Patient's knowledge and perception on the side effects of NSAIDs were recorded. RESULT: Fifty-four percent of the patients obtained information regarding the side effect of NSAIDs either from the rheumatologist, rheumatology staff nurse or other medical staffs (75.4%). The remaining 45.8% were naive of such knowledge. Fifteen percent obtained the information by surfing the internet and 9.2% from printed media. Twenty-four (24.2%) patients, experienced indigestion and/or stomach discomfort attributed to NSAIDs used. Two patients (1.7%) had hematemesis and malena once. CONCLUSION: This study shows that half of the patients who attended the rheumatology clinic were unaware of the side effect of NSAIDs. Available data showed that most of the knowledgeable patients are more conscience and self-educated. This study also reveals the important roles of clinicians, trained staff nurses as well as the pharmacist in providing the guidance and knowledge of any medication taken by patients.

Novel multiple apoptotic mechanism of shikonin in human glioma cells.

BACKGROUND: Shikonin is the main naphthoquinone compound of the root of Lithospermum erythrorhizon. Our previous study demonstrated that shikonin possesses anticancer activity in human hepatoma cells. However, the anticancer mechanism of shikonin in human glioma cells is unclear at present. In the present study, we demonstrated that shikonin induces apoptosis in three human glioma cell lines: U87MG, Hs683, and M059K cells. METHODS: Cell cycle, generation of reactive oxygen species (ROS), depletion of glutathione (GSH), and disruption of mitochondrial transmembrane potential in shikonin-treated cells were determined by flow cytometry. Apoptosis-related proteins, catalase, and superoxide dismutase-1 (SOD-1) were determined by Western blot testing. N-acetylcysteine (NAC), pifithrin-α (PFT-α), or cyclosporin A were applied to evaluate the molecular mechanism of shikonin in apoptosis. RESULTS: Shikonin induces the generation of ROS, depletion of GSH, disruption of mitochondrial transmembrane potential, upregulation of p53, and cleavage of PARP [poly(ADP-ribose) polymerase] in U87MG glioma cells. Moreover, shikonin causes catalase downregulation and SOD-1 upregulation as well as decreased Bcl-2 and increased Bax expression. Pretreatment with NAC, PFT-α, or cyclosporin A causes the recovery of shikonin-induced apoptosis. The ROS generation and GSH depletion induced by shikonin trigger mitochondrial transmembrane potential disruption. ROS production was partially dependent on the upregulation of p53 upon shikonin treatment. CONCLUSIONS: These studies are the first to show that shikonin-induced apoptosis occurs through multiple pathways in human glioma cells. We conclude that shikonin may be used as a potential chemotherapeutic agent against human glioma.

Osteoarticular tuberculosis mimicking rheumatoid arthritis.

Tuberculosis (TB) remains a global burden despite extensive efforts to control it. TB arthritis commonly manifest as monoarthritis of weight-bearing joints. We report a rare presentation of osteoarticular TB involving multiple small joints of the hands, which mimicked rheumatoid arthritis (RA). Magnetic resonance imaging showed tenosynovitis. The patient was initially treated for seronegative RA but failed to respond. Subsequently, synovial biopsy led to the diagnosis. Antituberculosis treatment was given for 1 year.

Molecular characterization of a novel trehalose-6-phosphate hydrolase, TreA, from Bacillus licheniformis.

An unidentified Bacillus licheniformis trehalose-6-phosphate hydrolase (BlTreA) gene was cloned and heterologously expressed in Escherichia coli M15 cells. The over-expressed BlTreA was purified to apparent homogeneity by metal-affinity chromatography and its molecular mass was determined to be approximately 65.9 kDa. The temperature and pH optima for BlTreA were 30 °C and 8.0, respectively. The enzyme hydrolyzed p-nitrophenyl-α-d-glucopyranoside (pNPG) and trehalose-6-phosphate efficiently, but it was inactive toward five other p-nitrophenyl derivatives. Steady-state kinetics with pNPG showed that BlTreA had a K(M) value of 5.2mM and a k(cat) value of 30.2s(-1). Circular dichroism analysis revealed that the secondary structures of BlTreA did not altered by 5-10% acetone and 10-20% ethanol, whereas 5-10% SDS had a detrimental effect on the folding of the enzyme. Thermal unfolding of this enzyme was found to be highly irreversible. The native enzyme started to unfold beyond ~0.14 M guanidine hydrochloride (GdnHCl) and reached the unfolded intermediates, [GdnHCl](0.5,N-I) and [GdnHCl](0.5,I-U), at 1.02 and 2.24 M, respectively. BlTreA was unfolded completely by 8M urea with [urea](0.5,N-U) of 4.98 M, corresponding to a free energy change of 4.29 kcal/mol for the N→U process. Moreover, the enzyme was unfolded by GdnHCl through a reversible pathway and the refolding reaction exhibited an intermediate state. Taken together, the characterization data provide a foundation for the future structure-function studies of BlTreA, a typical member of glycoside hydrolase family 13.

Contribution of conserved Glu255 and Cys289 residues to catalytic activity of recombinant aldehyde dehydrogenase from Bacillus licheniformis.

Based on the sequence homology, we have modeled the three-dimensional structure of Bacillus licheniformis aldehyde dehydrogenase (BlALDH) and identified two different residues, Glu255 and Cys289, that might be responsible for the catalytic function of the enzyme. The role of these residues was further investigated by site-directed mutagenesis and biophysical analysis. The expressed parental and mutant proteins were purified by nickel-chelate chromatography, and their molecular masses were determined to be approximately 53 kDa by SDS-PAGE. As compared with the parental BlALDH, a dramatic decrease or even complete loss of the dehydrogenase activity was observed for the mutant enzymes. Structural analysis showed that the intrinsic fluorescence and circular dichroism spectra of the mutant proteins were similar to the parental enzyme, but most of the variants exhibited a different sensitivity towards thermal- and guanidine hydrochloride-induced denaturation. These observations indicate that residues Glu255 and Cys289 play an important role in the dehydrogenase activity of BlALDH, and the rigidity of the enzyme has been changed as a consequence of the mutations.

Discovering amino acid patterns on binding sites in protein complexes.

Discovering amino acid (AA) patterns on protein binding sites has recently become popular. We propose a method to discover the association relationship among AAs on binding sites. Such knowledge of binding sites is very helpful in predicting protein-protein interactions. In this paper, we focus on protein complexes which have protein-protein recognition. The association rule mining technique is used to discover geographically adjacent amino acids on a binding site of a protein complex. When mining, instead of treating all AAs of binding sites as a transaction, we geographically partition AAs of binding sites in a protein complex. AAs in a partition are treated as a transaction. For the partition process, AAs on a binding site are projected from three-dimensional to two-dimensional. And then, assisted with a circular grid, AAs on the binding site are placed into grid cells. A circular grid has ten rings: a central ring, the second ring with 6 sectors, the third ring with 12 sectors, and later rings are added to four sectors in order. As for the radius of each ring, we examined the complexes and found that 10Å is a suitable range, which can be set by the user. After placing these recognition complexes on the circular grid, we obtain mining records (i.e. transactions) from each sector. A sector is regarded as a record. Finally, we use the association rule to mine these records for frequent AA patterns. If the support of an AA pattern is larger than the predetermined minimum support (i.e. threshold), it is called a frequent pattern. With these discovered patterns, we offer the biologists a novel point of view, which will improve the prediction accuracy of protein-protein recognition. In our experiments, we produced the AA patterns by data mining. As a result, we found that arginine (arg) most frequently appears on the binding sites of two proteins in the recognition protein complexes, while cysteine (cys) appears the fewest. In addition, if we discriminate the shape of binding sites between concave and convex further, we discover that patterns {arg, glu, asp} and {arg, ser, asp} on the concave shape of binding sites in a protein more frequently (i.e. higher probability) make contact with {lys} or {arg} on the convex shape of binding sites in another protein. Thus, we can confidently achieve a rate of at least 78%. On the other hand {val, gly, lys} on the convex surface of binding sites in proteins is more frequently in contact with {asp} on the concave site of another protein, and the confidence achieved is over 81%. Applying data mining in biology can reveal more facts that may otherwise be ignored or not easily discovered by the naked eye. Furthermore, we can discover more relationships among AAs on binding sites by appropriately rotating these residues on binding sites from a three-dimension to two-dimension perspective. We designed a circular grid to deposit the data, which total to 463 records consisting of AAs. Then we used the association rules to mine these records for discovering relationships. The proposed method in this paper provides an insight into the characteristics of binding sites for recognition complexes.

Adult-Onset Still's Disease: A Case Report.

Adult-onset Still's disease (AOSD) is a rare clinical entity with unknown etiology, characterized by arthritis, fever, evanescent rash and other systemic presentations. This report described a 45-year-old male who presented with sore throat, fever, arthritis, evanescent rash, raised liver enzymes and hyperferritinemia. He was diagnosed to have AOSD based on Yamuguchi criteria after the exclusion of other potential diagnoses. The patient partially responded to combined celecoxib and prednisolone. He was also prescribed methotrexate and his symptoms improved.

Contribution of Ser463 residue to the enzymatic and autoprocessing activities of Escherichia coli gamma-glutamyltranspeptidase.

A serine residue Ser463, required for proper function of E. coli y-glutamyltranspeptidase (EcGGT) was identified by site-directed mutagenesis on the basis of sequence alignment of human, pig, rat, and three bacterial enzymes. Thr-, Asp-, and Lys-substituted variants were overexpressed in E. coli M15 cells and the recombinant proteins were purified to near homogeneity by nickel-chelate chromatography. With the exception of S463T, the other two variants completely lost GGT activity, implying the importance of this residue in EcGGT. Moreover, substitution of Ser463 with either Lys or Asp impaired the capability of autocatalytic processing of the precursor into alpha- and beta-subunit. Computer modeling showed that the critical bonding distance of Gln390 C-Thr391 OG1 was significantly increased in S463D and S463K, indicating that these distance changes might be responsible for the lack of enzyme maturation. Measurements of intrinsic tryptophan fluorescence revealed alteration of the microenvironment of aromatic amino acid residues in S463D and S463K, while circular dichroism (CD) spectra were nearly identical for wild-type and all mutant enzymes. The temperature-dependent signal in the far-UV region for S463T was consistent with that of wild-type enzyme, but S463D and S463K showed a different sensitivity towards temperature-induced denaturation. These results implied that a significant conformational change occurred as a result of Asp- and Lys-substitution.

Role of the conserved Thr399 and Thr417 residues of Bacillus licheniformis gamma-Glutamyltranspeptidase as evaluated by mutational analysis.

Role of the conserved Thr399 and Thr417 residues of Bacillus licheniformis gamma-glutamyltranspeptidase (BlGGT) was investigated by site-directed mutagenesis. Substitutions of Thr399 and Thr417 of BlGGT with Ser resulted in a dramatic reduction in enzymatic activity. A complete loss of the GGT activity was observed in T399A, T399C, T417A, and T417K mutant enzymes. Furthermore, mutations on these two residues impaired the capability of autocatalytic processing of the enzyme. In vitro maturation experiments showed that BlGGT mutant precursors, pro-T399S, pro-T417S, and pro-T417A, could precede a time-dependent autocatalytic process to generate the 44.9- and 21.7-kDa subunits; however, the processed T417A had no enzymatic activity. Measurement of intrinsic tryptophan fluorescence revealed alteration of the microenvironment of aromatic amino acid residues, while Far-UV circular dichroism spectra were nearly identical for wild-type and mutant enzymes. These results suggest that residues Thr399 and Thr417 are important for BlGGT in the enzymatic maturation and reaction.

Role of the invariant Asn345 and Asn435 residues in a leucine aminopeptidase from Bacillus kaustophilus as evaluated by site-directed mutagenesis.

Role of the conserved Asn345 and Asn435 residues of Bacillus kaustophilus leucine aminopeptidase (BkLAP) was investigated by performing computer modeling and site-directed mutagenesis. Replacement of BkLAP Asn345 with Gln or Leu resulted in a dramatic reduction in enzymatic activity. A complete loss of the LAP activity was observed in Asn435 variants. Circular dichroism spectra were nearly identical for wild-type and all mutant enzymes, while measurement of intrinsic tryptophan fluorescence revealed the significant alterations of the microenvironment of aromatic amino acid residues in Asn345 and Asn435 replacements. Except for N435R and N435L, wild-type and other mutant enzymes showed a similar sensitivity towards temperature-induced denaturation. Computer modeling of the active-site structures of wild-type and mutant enzymes exhibits a partial or complete loss of the hydrogen bonding in the variants.

Purification, identification, and characterization of peanut isocitrate lyase.

Isocitrate lyase (ICL, EC 4.1.3.1) is commonly present in oil-rich seeds in catalyzing the cleavage of isocitrate to glyoxylate and succinate and plays an essential role in lipid metabolism and gluconeogenesis. When peanut kernels (Tainan 14) were germinated at 30 degrees C, the cotyledon ICL activities increased substantially in the initial 4 days, and the 4-day-germinated cotyledons were subjected to ICL purification by Tris-HCl buffer extraction, heat treatment at 55 degrees C for 1 h, (NH4)2SO4 fractionation at 25-35% saturation, DEAE-cellulose chromatography, and Sephacryl S-300 gel filtration. A single 64 kDa SDS-PAGE protein band was obtained with 7.7% recovery and 37.5-fold purity. It was identified as ICL by LC-MS/MS analyses and Mascot Search with 494 as the highest Probability Based Mowse Score (PBMS). On the basis of the sequence of the homologous ICL of Glycine max, 26% of the peptide sequences of the peanut ICL were identified. During gel filtration, separation of peanut catalase (identified by LC-MS/MS and Mascot Search with 405 as the highest PBMS) from peanut ICL was achieved. The highest measured peanut ICL enzymatic activities were obtained at 45 degrees C and pH 7.0-7.8, respectively. The enzyme activities were stable (>80%) as stored for 8 h at 30 degrees C, 15 days at 4 degrees C, or 60 days at -25 degrees C. As affected by the supplements in the reactants for activity determinations, ICL activity was not affected by glucose up to 4%, sucrose up to 5%, or ethanol up to 8.33%.

The anticancer effect of protein-extract from Bidens alba in human colorectal carcinoma SW480 cells via the reactive oxidative species- and glutathione depletion-dependent apoptosis.

Bidens alba has been used for healing cuts, injuries, swellings, hypertension, jaundice, and diabetes in some countries. However, the effect of B. alba on human cancer remains poorly understood. The goal of this study was to investigate whether B. alba protein-extract could have an anticancer property against human colorectal cancer. The human colorectal cancer SW 480 cells treated with the protein-extract of B. alba would cause marked DNA damages and apoptosis-related cellular morphologies. Treatment with 225 microg/ml B. alba protein-extract also led to the SW480 cells to produce readily intracellular reactive oxygen species (ROS) after 1h of treatment and last to 24 h. The intracellular glutathione (GSH) depletion occurred after 12-24h of treatment. The treatment of the protein-extract would also caused mitochondrial transmembrane potential (DeltaPsi(m)) to decrease and cytosolic cytochrome c to increase. The caspase 3/7 activities were activated from 3 to 6 h after the treatment. The percentages of apoptosis induced by the protein-extract of B. alba decreased 26.4%, 10.1%, and 29.4% when the SW 480 cells were pretreated with Vitamin C, N-acetylcysteine, and Boc-Asp(OMe)-fmk, respectively. Taken together, we demonstrated for the first time that the protein-extract of B. alba could induce apoptosis that was related to the ROS production and GSH depletion in human colorectal cancer. The protein-extract of B. alba might have therapeutic value against the human colorectal cancer.

Residues Arg114 and Arg337 are critical for the proper function of Escherichia coli gamma-glutamyltranspeptidase.

To evaluate the importance of conserved Arg114 and Arg337 residues of Escherichia coli gamma-glutamyltranspeptidase (EcGGT), Lys, Leu, or Asp-substituted mutants were constructed by site-directed mutagenesis. The wild-type and mutant enzymes were overexpressed in the recombinant E. coli M15 and purified by nickel-chelate chromatography to near homogeneity. With the exception of R114K, all the other mutants significantly lost GGT activity, confirming the importance of these two residues in EcGGT. Kinetic analysis of R114L, R114D, R337K, and R337L revealed a significant increase in K(m) with a minor change in k(cat), leading to more than an 8-fold decrease in k(cat)/K(m) values. Mutations of Arg337 impaired the capability of autocatalytic processing of the enzyme. In vitro maturation experiments revealed that EcGGT precursor mutants, pro-R337K and pro-R337L, could precede a time-dependent autocatalytic process to generate the small and large subunits, while no autocatalytic processing was observed in pro-R337D. Computer modeling showed that the critical bonding distance of Gln390 O-Thr391 HG1 and Gln390 C-Thr391 OG1 are significantly increased in Arg337 replacements, implying that these distance changes might be responsible for the lack of enzyme maturation.