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1.
J Pediatr Gastroenterol Nutr ; 75(5): 623-628, 2022 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-35767565

RESUMO

OBJECTIVES: To analyze demographic, psychosocial, and clinical factors in pediatric liver transplant recipients for their association with death or loss to follow up in adulthood. We aimed to better understand known health disparities in transplant outcomes and identify potentially modifiable risk factors prior to transfer. METHODS: A retrospective cohort study of children who underwent liver transplantation at a large tertiary transplant center and were transferred to adult care between 2000 and 2015. RESULTS: During the study period, 101 qualifying patients were transferred. Ninety-three individuals followed with an adult provider, while 8 were lost to follow up. In total 23 of 93 patients died after transfer (24.7%). Several childhood factors were associated with adult death: Black race [odds ratio (OR) 6.59, P < 0.001]; psychiatric illness or substance use (OR 2.81, P = 0.04); failure to graduate high school before transfer (OR 9.59, P < 0.001); posttransplant tacrolimus medication-level variability index >2.5 (OR 5.36, P = 0.04); provider documentation of medication nonadherence (OR 4.72, P = 0.02); acute cellular rejection (OR 4.44, P = 0.03); the presence of diabetes mellitus (OR 5.71, P = 0.001), and chronic kidney disease (OR 2.82, P = 0.04). Failure to graduate HS was associated with loss to follow up ( P < 0.001). On multivariate analysis, Black race, substance use, diabetes, and failure to graduate HS retained association with adult death (each P < 0.05). CONCLUSIONS: Complex, intertwined patient characteristics are associated with increased odds of death in pediatric liver transplant recipients transferred to adult care. Early recognition of high-risk patients and intervention for modifiable factors, such as improved HS graduation and substance use prevention, may improve long-term outcomes.


Assuntos
Diabetes Mellitus , Transplante de Fígado , Transtornos Relacionados ao Uso de Substâncias , Adulto , Humanos , Criança , Transplante de Fígado/efeitos adversos , Sobrevivência de Enxerto , Estudos Retrospectivos , Rejeição de Enxerto/epidemiologia , Fatores de Risco , Adesão à Medicação , Diabetes Mellitus/etiologia , Transtornos Relacionados ao Uso de Substâncias/etiologia , Transplantados/psicologia
2.
J Pediatr ; 233: 119-125.e1, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33667506

RESUMO

OBJECTIVE: To analyze the long-term outcomes in pediatric liver transplant recipients after they have transferred to an adult provider and assess for racial disparities in health outcomes. STUDY DESIGN: This is a single-center, retrospective review of pediatric patients who underwent liver transplantation between July 1990 and August 2015 at a tertiary healthcare system with a large transplant center. Patient mortality and retransplantation were assessed after transfer to adult care. RESULTS: There were 120 patients who were transferred, of whom 19 did not meet the inclusion criteria. Of the remaining 101 patients, 64 (63%) transferred care to a nearby affiliated tertiary adult facility, 29 (29%) were followed by other healthcare systems, and 8 (8%) were lost to follow-up. Of the patients followed at our affiliated adult center, 18 of the 64 (28%) died. Of those 18 deaths, 4 (22%) occurred within the first 2 years after transfer, and 10 (55%) within 5 years of transfer. Four patients were retransplanted by an adult provider, of whom 2 eventually received a third transplant. African Americans had higher rates of death after transfer than patients of other races (44% mortality vs 16%, representing 67% of all cases of death; P = .032), with nearly 50% mortality at 20 years from time of transplantation. CONCLUSIONS: Death is common in pediatric liver transplant recipients after transfer to adult care, with African Americans having disproportionately higher mortality. This period of transition of care is a vulnerable time, and measures must be taken to ensure the safe transfer of young adults with chronic health care needs.


Assuntos
Negro ou Afro-Americano , Hepatopatias/mortalidade , Transplante de Fígado , Transição para Assistência do Adulto , Transplantados , Adolescente , Adulto , Criança , Estudos de Coortes , Feminino , Rejeição de Enxerto/epidemiologia , Rejeição de Enxerto/cirurgia , Humanos , Hepatopatias/cirurgia , Masculino , Reoperação/estatística & dados numéricos , Estudos Retrospectivos , Estados Unidos/epidemiologia , Adulto Jovem
3.
Pediatr Transplant ; 25(5): e13978, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33522659

RESUMO

Recurrent autoimmune hepatitis (rAIH) occurs in patients who undergo liver transplantation (LT) for AIH and de novo AIH (dAIH) is seen in patients who are transplanted for etiologies other than AIH. Whether these are distinct diseases with a similar phenotype remains understudied. The aim of this study was to identify clinical and immunologic factors affecting outcome in patients with dAIH and rAIH. A retrospective review of 387 LT patients from 1997 to 2014 was carried out, and they were followed until 2018. Patients with rAIH or dAIH were identified based on the pre-transplant diagnosis of AIH (or not) and characteristic histology. Liver biopsies were stained with H&E, B-cell marker CD20, and plasma cell marker CD138. Out of 387 patients, 31 were transplanted for AIH, and 8/31 developed rAIH. Of the remaining 356 patients, eight developed dAIH. Compared to the dAIH group, rAIH occurred in older patients, had an earlier onset in the allograft, and had higher IgG and serum ALT levels. It was most commonly seen in African American (AA) patients (87%). rAIH patients had significantly higher CD20 and CD138 positivity in liver biopsies. In addition, they had increased rejection episodes prior to the onset of recurrence, increased graft loss, and mortality. rAIH is a more aggressive disease, and has a preponderance of B cells and plasma cells in the liver tissue as compared to dAIH. The concurrent association with increased graft loss and patient mortality in rAIH warrants further investigations into B cell-targeted therapies.


Assuntos
Hepatite Autoimune/etiologia , Transplante de Fígado , Complicações Pós-Operatórias/etiologia , Adolescente , Biomarcadores/metabolismo , Estudos de Casos e Controles , Criança , Pré-Escolar , Progressão da Doença , Feminino , Seguimentos , Sobrevivência de Enxerto , Hepatite Autoimune/diagnóstico , Hepatite Autoimune/metabolismo , Hepatite Autoimune/patologia , Humanos , Fígado/metabolismo , Fígado/patologia , Masculino , Avaliação de Resultados em Cuidados de Saúde , Complicações Pós-Operatórias/diagnóstico , Complicações Pós-Operatórias/metabolismo , Complicações Pós-Operatórias/patologia , Recidiva , Estudos Retrospectivos , Fatores de Risco
4.
Curr Gastroenterol Rep ; 23(3): 3, 2021 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-33523312

RESUMO

PURPOSE OF REVIEW: Many pediatric liver transplant patients are surviving to adulthood, and providers have come to recognize the importance of effectively transitioning these patients to an adult hepatologist. The review aims to analyze the most recent literature regarding patient outcomes after transition, barriers to successful transition, recommendations from clinicians and medical societies regarding transition programs, and to provide personal insights from our experience in transitioning liver transplant recipients. RECENT FINDINGS: While results were variable between studies, many recent reports show significant morbidity and mortality in patients following transition to adult care. Medical non-adherence is frequently seen in adolescents and young adults both prior to and after transition, and is consistently associated with higher rates of rejection, graft loss, and death. In general, transplant programs with a formal transition process had better patient outcomes though recent findings are mostly-single center and direct comparison between programs is difficult. Societal recommendations for how to create a transition program contain a number of common themes that we have categorized for easier understanding. Successful transition is vital to the continued health of pediatric liver transplant patients. While an effective transition program includes a number of key components, it should be individualized to best function within a given transplant center. Here, we have reviewed a number of recent single-center retrospective studies on transition, but multi-site retrospective or prospective data is lacking, and is a fertile area for future research.


Assuntos
Transplante de Fígado , Transição para Assistência do Adulto , Adolescente , Adulto , Criança , Humanos , Estudos Prospectivos , Estudos Retrospectivos , Adulto Jovem
6.
J Med Internet Res ; 21(10): e13499, 2019 10 21.
Artigo em Inglês | MEDLINE | ID: mdl-31638592

RESUMO

BACKGROUND: Poor medication adherence is common; however, few mechanisms exist in clinical practice to monitor how patients take medications in outpatient settings. OBJECTIVE: This study aimed to pilot test the Electronic Medication Complete Communication (EMC2) strategy, a low-cost, sustainable approach that uses functionalities within the electronic health record to promote outpatient medication adherence and safety. METHODS: The EMC2 strategy was implemented in 2 academic practices for 14 higher-risk diabetes medications. The strategy included: (1) clinical decision support alerts to prompt provider counseling on medication risks, (2) low-literacy medication summaries for patients, (3) a portal-based questionnaire to monitor outpatient medication use, and (4) clinical outreach for identified concerns. We recruited adult patients with diabetes who were prescribed a higher-risk diabetes medication. Participants completed baseline and 2-week interviews to assess receipt of, and satisfaction with, intervention components. RESULTS: A total of 100 patients were enrolled; 90 completed the 2-week interview. Patients were racially diverse, 30.0% (30/100) had a high school education or less, and 40.0% (40/100) had limited literacy skills. About a quarter (28/100) did not have a portal account; socioeconomic disparities were noted in account ownership by income and education. Among patients with a portal account, 58% (42/72) completed the questionnaire; 21 of the 42 patients reported concerns warranting clinical follow-up. Of these, 17 were contacted by the clinic or had their issue resolved within 24 hours. Most patients (33/38, 89%) who completed the portal questionnaire and follow-up interview reported high levels of satisfaction (score of 8 or greater on a scale of 1-10). CONCLUSIONS: Findings suggest that the EMC2 strategy can be reliably implemented and delivered to patients, with high levels of satisfaction. Disparities in portal use may restrict intervention reach. Although the EMC2 strategy can be implemented with minimal impact on clinic workflow, future trials are needed to evaluate its effectiveness to promote adherence and safety.


Assuntos
Sistemas de Apoio a Decisões Clínicas/normas , Diabetes Mellitus/tratamento farmacológico , Registros Eletrônicos de Saúde/normas , Idoso , Feminino , Humanos , Estudos Longitudinais , Masculino , Adesão à Medicação , Pessoa de Meia-Idade , Projetos Piloto
7.
Ther Innov Regul Sci ; 53(1): 100-109, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29714598

RESUMO

BACKGROUND: Print pharmaceutical advertisements in the United States require inclusion of a brief summary of side effects, warnings, precautions, and contraindications from the labeling. The full package insert, which sponsors have traditionally used to fulfill the brief summary requirement, does not adhere to health literacy best practices, limiting its value to consumers. This study compared the understandability and usability of brief summaries in 3 formats designed to be more consumer friendly. METHODS: Three brief summary formats were tested: (1) 2-column "Question and Answer"; (2) "Prescription Drug Facts Box," similar to current US over-the-counter drug facts labeling; and (3) "Health Literacy," based on clear communication principles. Researchers evaluated the formats using the Suitability Assessment of Materials (SAM) tool and conducted structured, scripted, one-on-one interviews (usability tests) with participants with estimated low to average education levels. This research was replicated across 2 therapeutic areas (type 2 diabetes and plaque psoriasis). RESULTS: SAM scores showed that the Health Literacy format outperformed the Question and Answer format and the Prescription Drug Facts Box format in both therapeutic areas, with both Health Literacy brief summaries rated on the SAM as "superior." Qualitative usability tests supported the SAM findings, with the Health Literacy format preferred consistently over the Question and Answer format, and more often than not over the Prescription Drug Facts Box format. CONCLUSIONS: Sponsors can employ a user-tested Health Literacy format to improve the understandability and usability of brief summaries with patients.


Assuntos
Rotulagem de Medicamentos , Letramento em Saúde , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Medicamentos sob Prescrição
8.
Metab Eng ; 52: 232-242, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30557615

RESUMO

Oligosaccharides present in human breast milk have been linked to beneficial effects on infant health. Inclusion of these human milk oligosaccharides (HMOs) in infant formula can recapitulate these health benefits. As a result, there is substantial commercial interest in a cost-effective source of HMOs as infant formula ingredients. Here we demonstrate that the yeast species Saccharomyces cerevisiae and Yarrowia lipolytica both can be engineered to produce 2'-fucosyllactose (2'FL), which is the most abundant oligosaccharide in human breast milk, at high titer and productivity. Both yeast species were modified to enable uptake of lactose and synthesis of GDP-fucose - the two precursors of 2'FL - by installing a lactose transporter and enzymes that convert GDP-mannose to GDP-fucose. Production of 2'FL was then enabled by expression of α-1,2-fucosyltransferases from various organisms. By screening candidate transporters from a variety of sources, we identified transporters capable of exporting 2'FL from yeast, which is a key consideration for any biocatalyst for 2'FL production. In particular, we identified CDT2 from Neurospora crassa as a promising target for further engineering to improve 2'FL efflux. Finally, we demonstrated production of 2'FL in fermenters at rates and titers that indicate the potential of engineered S. cerevisiae and Y. lipolytica strains for commercial 2'FL production.


Assuntos
Engenharia Metabólica/métodos , Leite Humano/química , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Trissacarídeos/biossíntese , Yarrowia/genética , Yarrowia/metabolismo , Feminino , Fermentação , Fucosiltransferases/genética , Fucosiltransferases/metabolismo , Guanosina Difosfato Fucose/biossíntese , Humanos , Lactose/biossíntese , Neurospora crassa/genética , Neurospora crassa/metabolismo , Galactosídeo 2-alfa-L-Fucosiltransferase
10.
J Clin Microbiol ; 46(9): 3087-90, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18650347

RESUMO

Identification of viridans group streptococci (VGS) to the species level is difficult because VGS exchange genetic material. We performed multilocus DNA target sequencing to assess phylogenetic concordance of VGS for a well-defined clinical syndrome. The hierarchy of sequence data was often discordant, underscoring the importance of establishing biological relevance for finer phylogenetic distinctions.


Assuntos
Endocardite Bacteriana/microbiologia , Infecções Estreptocócicas/microbiologia , Estreptococos Viridans/genética , Humanos , Filogenia , Análise de Sequência de DNA
11.
Fungal Genet Biol ; 45(3): 180-9, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17656140

RESUMO

An acyl-CoA dehydrogenase has been identified as part of the mitochondrial beta-oxidation pathway in the ascomycete fungus Aspergillus nidulans. Disruption of the scdA gene prevented use of butyric acid (C(4)) and hexanoic acid (C(6)) as carbon sources and reduced cellular butyryl-CoA dehydrogenase activity by 7.5-fold. While the mutant strain exhibited wild-type levels of growth on erucic acid (C(22:1)) and oleic acid (C(18:1)), some reduction in growth was observed with myristic acid (C(14)). The DeltascdA mutation was found to be epistatic to a mutation downstream in the beta-oxidation pathway (disruption of enoyl-CoA hydratase). The DeltascdA mutant was also unable to use isoleucine or valine as a carbon source. Transcription of scdA was observed in the presence of either fatty acids or amino acids. When the mutant was grown in medium containing either isoleucine or valine, organic acid analysis of culture supernatants showed accumulation of 2-oxo acid intermediates of branched chain amino acid catabolism, suggesting feedback inhibition of the upstream branched-chain alpha-keto acid dehydrogenase.


Assuntos
Acil-CoA Desidrogenases/metabolismo , Aspergillus nidulans/metabolismo , Ácidos Graxos/metabolismo , Isoleucina/metabolismo , Valina/metabolismo , Acil Coenzima A/química , Acil Coenzima A/metabolismo , Acil-CoA Desidrogenases/genética , Aspergillus nidulans/genética , Ácidos Erúcicos/química , Ácidos Erúcicos/metabolismo , Ácidos Graxos/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Teste de Complementação Genética , Isoleucina/química , Estrutura Molecular , Mutação , Ácido Mirístico/química , Ácido Mirístico/metabolismo , Ácido Oleico/química , Ácido Oleico/metabolismo , Oxirredução , Transcrição Gênica
12.
Chem Biol ; 13(1): 31-7, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16426969

RESUMO

The genus Aspergillus is renowned for its ability to produce a myriad of bioactive secondary metabolites. Although the propensity of biosynthetic genes to form contiguous clusters greatly facilitates assignment of putative secondary metabolite genes in the completed Aspergillus genomes, such analysis cannot predict gene expression and, ultimately, product formation. To circumvent this deficiency, we have examined Aspergillus nidulans microarrays for expressed secondary metabolite gene clusters by using the transcriptional regulator LaeA. Deletion or overexpression of laeA clearly identified numerous secondary metabolite clusters. A gene deletion in one of the clusters eliminated the production of the antitumor compound terrequinone A, a metabolite not described, from A. nidulans. In this paper, we highlight that LaeA-based genome mining helps decipher the secondary metabolome of Aspergilli and provides an unparalleled view to assess secondary metabolism gene regulation.


Assuntos
Aspergillus nidulans/genética , Aspergillus nidulans/metabolismo , Produtos Biológicos/genética , Genes Fúngicos/genética , Genômica , Produtos Biológicos/isolamento & purificação , Regulação Fúngica da Expressão Gênica/genética , Indóis/química , Indóis/metabolismo , Estrutura Molecular , Família Multigênica/genética , Mutação/genética , Análise de Sequência com Séries de Oligonucleotídeos
13.
Mol Plant Microbe Interact ; 18(8): 783-93, 2005 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16134890

RESUMO

Seed contamination with polyketide mycotoxins, including aflatoxin (AF) and sterigmatocystin (ST) produced by Aspergillus spp., is an agricultural, economic, and medical issue worldwide. Acetyl-CoA, the fundamental building block of all known fungal polyketides, is generated by a large number of biochemical pathways, including beta-oxidation of fatty acids and glycolysis of sugars. We present several lines of evidence to support a major role for seed fatty acids in formation of AF and ST in A. flavus, A. parasiticus, and A. nidulans. Aspergillus strains exhibiting canonical signs of oleic acid-induced peroxisome proliferation, including increased catalase activity, beta-oxidation gene expression, and peroxisomal clustering, also exhibited a marked increase in toxin gene expression and biosynthesis. Furthermore, microscopic observations showed that the ST and AF precursor norsolorinic acid accumulated in peroxisomes of all three Aspergilli. While a peroxisomal beta-oxidation mutation eliminated oleic acid-induced increases in ST in A. nidulans, a mitochondrial beta-oxidation mutation played a larger role in eliminating ST formation on oatmeal medium and on live corn kernels, implicating a fundamental role for both peroxisomal and mitochondrial beta-oxidation in toxin production.


Assuntos
Aflatoxinas/biossíntese , Aspergillus/metabolismo , Ácidos Graxos/metabolismo , Plantas/metabolismo , Plantas/microbiologia , Esterigmatocistina/biossíntese , Antraquinonas/metabolismo , Aspergillus/citologia , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Regulação Enzimológica da Expressão Gênica , Regulação Fúngica da Expressão Gênica , Mitocôndrias/metabolismo , Mutação , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Peroxissomos/metabolismo , Transcrição Gênica
15.
Mol Microbiol ; 54(5): 1173-85, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15554960

RESUMO

Beta-oxidation (beta-ox) occurs exclusively in the peroxisomes of Saccharomyces cerevisiae and other yeasts, leading to the supposition that fungi lack mitochondrial beta-ox. Here we present unequivocal evidence that the filamentous fungus Aspergillus nidulans houses both peroxisomal and mitochondrial beta-ox. While growth of a peroxisomal beta-ox disruption mutant (DeltafoxA) was eliminated on a very long-chain fatty acid (C(22:1)), growth was only partially impeded on a long-chain fatty acid (C(18:1)) and was not affected at all on short chain (C4-C6) fatty acids. In contrast, growth of a putative enoyl-CoA hydratase mutant (DeltaechA) was abolished on short-chain and severely restricted on long- and very long-chain fatty acids. Furthermore fatty acids inhibited growth of the DeltaechA mutant but not the DeltafoxA mutant in the presence of an alternate carbon source (lactose). Disruption of echA led to a 28-fold reduction in 2-butenoyl-CoA hydratase activity in a preparation of organelles. EchA was also required for growth on isoleucine and valine. The subcellular localization of the FoxA and EchA proteins was confirmed through the use of red and green fluorescent protein fusions.


Assuntos
Aspergillus nidulans/enzimologia , Ácidos Graxos/metabolismo , Mitocôndrias/enzimologia , Complexos Multienzimáticos/isolamento & purificação , Acil Coenzima A/metabolismo , Aspergillus nidulans/química , Aspergillus nidulans/crescimento & desenvolvimento , Aspergillus nidulans/metabolismo , Enoil-CoA Hidratase/genética , Enoil-CoA Hidratase/fisiologia , Proteínas Fúngicas/genética , Proteínas Fúngicas/isolamento & purificação , Proteínas Fúngicas/metabolismo , Deleção de Genes , Genes Fúngicos , Genes Reporter , Proteínas de Fluorescência Verde/análise , Proteínas de Fluorescência Verde/genética , Isoleucina/metabolismo , Lactose/metabolismo , Proteínas Luminescentes/análise , Proteínas Luminescentes/genética , Mitocôndrias/metabolismo , Proteína Mitocondrial Trifuncional , Complexos Multienzimáticos/genética , Complexos Multienzimáticos/metabolismo , Oxirredução , Peroxissomos/enzimologia , Peroxissomos/metabolismo , Proteínas Recombinantes de Fusão/análise , Proteínas Recombinantes de Fusão/genética , Valina/metabolismo , Proteína Vermelha Fluorescente
16.
Microbiology (Reading) ; 150(Pt 5): 1385-1395, 2004 May.
Artigo em Inglês | MEDLINE | ID: mdl-15133100

RESUMO

In Salmonella enterica, the last step of the synthesis of adenosylcobamide is catalysed by the cobalamin synthase enzyme encoded by the cobS gene of this bacterium. Overexpression of the S. enterica cobS gene in Escherichia coli elicited the accumulation of the phage shock protein PspA, a protein whose expression has been linked to membrane stress. Resolution of inner and outer membranes of S. enterica by isopycnic density ultracentrifugation showed CobS activity associated with the inner membrane, a result that was confirmed using antibodies against CobS. Computer analysis of the predicted amino acid sequence of CobS suggested it was an integral membrane protein. Results of experiments performed with strains carrying plasmids encoding CobS-alkaline phosphatase or CobS-beta-galactosidase protein fusions were consistent with the membrane localization of the CobS protein. Modifications to the predicted model were made based on data obtained from experiments using protein fusions. The function encoded by the cobS orthologue in the methanogenic archaeon Methanobacterium thermoautotrophicum strain deltaH compensated for the lack of CobS during cobalamin synthesis in cobS strains of S. enterica. Cobalamin synthase activity was also detected in a membrane preparation of M. thermoautotrophicum. It was concluded that the assembly of the nucleotide loop of adenosylcobamides in archaea and bacteria is a membrane-associated process. Possible reasons for the association of adenosylcobamide biosynthetic enzymes with the cell membrane are discussed.


Assuntos
Membrana Celular/enzimologia , Cobamidas/biossíntese , Escherichia coli/enzimologia , Methanobacterium/enzimologia , Transferases de Grupos Nitrogenados/metabolismo , Salmonella enterica/enzimologia , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cobamidas/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Transferases de Grupos Nitrogenados/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Ultracentrifugação
17.
Org Lett ; 5(13): 2211-3, 2003 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-12816411

RESUMO

Dimethylbezimidazole, the axial ligand of vitamin B(12), is synthesized from riboflavin by a two-electron oxidation, a retro-aldol condensation, and a second two-electron oxidation. This oxidative cascade readily takes place nonenzymatically under physiological conditions. [reaction: see text]


Assuntos
Benzimidazóis/síntese química , Cobamidas/metabolismo , Benzimidazóis/química , Benzimidazóis/metabolismo , Cromatografia Líquida de Alta Pressão , Ligantes , Oxirredução , Riboflavina/química
18.
Microbiology (Reading) ; 149(Pt 4): 983-990, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-12686640

RESUMO

The CobT enzyme of Salmonella typhimurium was shown in vitro to have NAD(+)-dependent ADPribosyltransferase activity. The CobT enzyme transferred the ADPribosyl moiety of NAD(+) onto 5,6-dimethylbenzimidazole (DMB) yielding a new dinucleotide, namely alpha-5,6-dimethylbenzimidazole adenine dinucleotide (alpha-DAD), whose identity was established by mass spectrometry. The N(1)-(alpha-D-ribosyl)-5,6-dimethylbenzimidazoyl moiety (alpha-ribazole) of alpha-DAD was incorporated into adenosylcobalamin (AdoCbl) by cell-free extracts of S. typhimurium, indicating that alpha-DAD served as an intermediate of AdoCbl biosynthesis. The rate of transfer of the ADPribosyl moiety was slower than the rate of transfer of the phosphoribosyl moiety of nicotinate mononucleotide (NaMN) to DMB. The CobT enzyme displayed a low K(m) for NaMN (0.51 mM) relative to the one for NAD(+) (9 mM); nicotinate adenine dinucleotide (NaAD) and nicotinamide mononucleotide (NMN) also served as substrates for CobT. In spite of the high K(m) of CobT for NAD(+), the latter is proposed to be a relevant physiological substrate of CobT, given that the intracellular concentrations of NaMN, NMN and NaAD in actively growing S. typhimurium are undetectable. Evidence shows that extracts of S. typhimurium contain an as-yet unidentified dinucleotide pyrophosphatase that can cleave alpha-DAD into alpha-ribazole-5'-P and AMP; alpha-ribazole-5'-P can then enter the AdoCbl biosynthetic pathway.


Assuntos
ADP Ribose Transferases/metabolismo , Nucleotídeos de Adenina/metabolismo , Benzimidazóis/metabolismo , Complexos Multienzimáticos/metabolismo , Nucleotidiltransferases/metabolismo , Pentosiltransferases/metabolismo , Salmonella typhimurium/enzimologia , Vitamina B 12/biossíntese , Cobamidas/metabolismo , Cinética , NAD/metabolismo , Ribonucleotídeos , Especificidade por Substrato
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