239,796 research outputs found
X-ray structure of a putative reaction intermediate of 5-aminolaevulinic acid dehydratase
No full textThe X-ray structure of yeast 5-aminolaevulinic acid dehydratase, in which the catalytic site of the enzyme is complexed with a putative cyclic intermediate composed of both substrate moieties, has been solved at 0.16 nm (1.6 Å) resolution. The cyclic intermediate is bound covalently to Lys(263) with the amino group of the aminomethyl side chain ligated to the active-site zinc ion in a position normally occupied by a catalytic hydroxide ion. The cyclic intermediate is catalytically competent, as shown by its turnover in the presence of added substrate to form porphobilinogen. The findings, combined with those of previous studies, are consistent with a catalytic mechanism in which the C–C bond linking both substrates in the intermediate is formed before the C–N bond
Acute intermittent porphyria in Sweden. Molecular, functional and clinical consequences of some new mutations found in the porphobilinogen deaminase gene
No full textAcute intermittent porphyria (AIP) is an autosomal dominant disorder caused by a partial deficit of porphobilinogen deaminase (PBGD), the third of eight enzymes in the haem biosynthetic pathway. The overt disease is characterized by neuropsychiatric symptoms that are often triggered by exogenous factors such as certain drugs, stress, and alcohol. The aim of this work has been to identify the underlying genetic defect in each AIP-affected family in order to provide early counselling to assist in the avoidance of precipitating factors. The prevalence of AIP in Sweden is in the order of 1:10 000. The major mutation in Sweden, W198X, is due to a founder effect in the northern part of the country. This mutation, together with a further 11 mutations, have been reported previously. The present communication encompasses the great majority of AIP kindreds in Sweden and includes a further 27 mutations within the PBGD gene. This includes 14 completely new mutations, as well as 11 known mutations detected for the first time in Sweden. The majority of the mutations are located in exons 10 and 12 with fewer in exon 7. The clinical and biochemical outcomes in some patients are described. We also use the three-dimensional structure of the porphobilinogen deaminase enzyme to predict the possible molecular and functional consequences of the new Swedish missense and nonsense mutations
Dimeric pig heart succinate-coenzyme A transferase uses only one subunit to support catalysis
No full textPig heart succinate-coenzyme A transferase (succinyl-coenzyme A: 3-oxoacid coenzyme A transferase; E. C. 2.8.3.5.), a dimeric enzyme purified by affinity chromatography on Procion Blue MX-2G Sepharose, reacts with acetoacetyl-coenzyme A to form a covalent enzyme-coenzyme A thiolester intermediate in which the active site glutamate (E344) of both subunits each forms thiolester links with coenzyme A. Reaction of this dimeric enzyme-coenzyme A species with sodium borohydride leads to inactivation of the enzyme and reduction of the thiolester on both subunits to the corresponding enzyme alcohol, as judged by electrospray mass spectrometry. Reaction of the dimeric enzyme-coenzyme A intermediate with either succinate or acetoacetate, however, results in only one-half of the coenzyme A being transferred to the acceptor carboxylate to form either succinyl-coenzyme A or acetoacetyl-coenzyme A. Reaction of this latter enzyme species with borohydride caused no loss of enzyme activity despite the reduction of the remaining half of the enzyme-coenzyme A thiolester to the enzyme alcohol. That this catalytic asymmetry existed between subunits within the same enzyme dimer was demonstrated by showing that the enzyme species, created by successive reaction with acetoacetyl-coenzyme A and succinate, bound to Blue MX-2G Sepharose through the remaining available active site and could be eluted as a single chromatographic species by succinyl-coenzyme A. It is concluded that while both of the subunits of the succinate-coenzyme A transferase dimer are able to form enzyme-coenzyme A thiolester intermediates, only one subunit is competent to transfer the coenzyme A moiety to a carboxylic acid acceptor to form the new acyl-coenzyme A product. The possible structural basis for this catalytic asymmetry and its mechanistic implications are discussed
Basha P. Jordan Oral History Interview
No full textDr. Basha P. Jordan and Dr. Antoinette Jackson discuss the Jordan Family legacy and their connection to Lincoln Cemetery. Dr. Basha P. Jordan is a Pastor and founder of Hope Alive Outreach. Dr. Jordan\u27s grandfather, Elder Jordan Sr., contributed towards advancing the Black community in St. Petersburg, Florida, through land donation. Following his grandfather\u27s footsteps, Dr. Jordan continues to work towards community development using his ministry, participation in the Lincoln Cemetery Board of Commissioners, the redevelopment of The Legacy at Jordan Park, and the production of a recovery radio. The conversation between Dr. Jackson and Dr. Jordan provides an overview of St. Petersburg\u27s Black history, particularly emphasizing the Jordan Family and the various churches in the area
5-Aminolaevulinic acid dehydratase: metals, mutants and mechanism
No full text5-Aminolaevulinic acid dehydratase catalyses the formation of porphobilinogen from two molecules of 5-aminolaevulinic acid. The studies described highlight the importance of a bivalent metal ion and two active-site lysine residues for the functioning of 5-aminolaevulinic acid dehydratase. Dehydratases fall into two main categories: zinc-dependent enzymes and magnesium-dependent enzymes. Mutations that introduced zinc-binding ligands into a magnesium-dependent enzyme conferred an absolute requirement for zinc. Mutagenesis of lysine residues 247 and 195 in the Escherichia coli enzyme lead to dramatic effects on enzyme activity, with lysine 247 being absolutely essential. Mutation of either lysine 247 or 195 to cysteine, and treatment of the mutant enzyme with 2-bromethylamine, resulted in the recovery of substantial enzyme activity. The effects of the site-directed alkylating inhibitor, 5-chlorolaevulinic acid, and 4,7-dioxosebacic acid, a putative intermediate analogue, were investigated by X-ray crystallography. These inhibitors reacted with both active-site lysine residues. The role of these two lysine residues in the enzyme mechanism is discussed
The x-ray structure of yeast 5-aminolaevulinic acid dehydratase complexed with substrate and three inhibitors
No full textThe structures of 5-aminolaevulinic acid dehydratase (ALAD) complexed with substrate (5-aminolaevulinic acid) and three inhibitors: laevulinic acid, succinylacetone and 4-keto-5-aminolaevulinic acid, have been solved at high resolution. The ligands all bind by forming a covalent link with Lys263 at the active site. The structures define the interactions made byone of the two substrate moieties that bind to the enzyme during catalysis. All of the inhibitors induce a significant ordering of the flap covering the active site. Succinylacetone appears to be unique by inducing a numberof conformational changes in loops covering the active site, which may be important for understanding the co-operative properties of ALAD enzymes. Succinylacetone is produced in large amounts by patients suffering from the hereditary disease type I tyrosinaemia and its potent inhibition of ALAD also has implications for the pathology of this disease. The most intriguing result is that obtained with 4-keto-5-aminohexanoic acid, which seems to form a stable carbinolamine intermediate with Lys263. It appears that we have defined the structure of an intermediateof Schiff base formation that the substrate forms upon binding to the P-site of the enzyme
[Correspondence Between D. P. D'Angelo and Barbara Jordan - May 1973]
No full textCorrespondence between D. P. D'Angelo and Barbara Jordan where D'Angelo requests that Jordan support a bill that would amend the Railroad Retirement Act and Interstate Commerce Act. Jordan confirms her support of the bill
Breastfeeding attitudes and knowledge among sixth year medical students in Jordan
No full textBackground: Previous reports have demonstrated that counseling about breastfeeding can improve the rate and initiation duration of breastfeeding. However, those medical students are ill-prepared for this role. It is unclear whether medical students would provide the knowledge and skills necessary for effective breastfeeding promotion or not in Jordan. The aim of this study was to identify breastfeeding attitudes and knowledge among 6th year medical students in their final year at The Jordan University of Science and Technology (JUST).Methods: A 28-item self-administered questionnaire; containing three sections: knowledge (13 items) attitude (7 items) and demographic (3 items), were distributed randomly to medical students. The random sample consisted of 234 medical students who were in their final year. The questionnaire assessed both breastfeeding attitudes and knowledge.Results: The results were explained taking into consideration gender and being a parent. Mean attitude's score for participants without children was 46.7 as compared to 44.0 for those with children. The results showed similar negative attitude toward breastfeeding among both male and female participants regardless of having children or not (p=0.35). This means that there were no significant difference in attitudes toward breastfeeding among male and female students whether they are having children or not. On the other hand, the mean knowledge score was 22.9 for male participants while it was 21.55 for female participants, indicating some degree of breastfeeding knowledge among participants (p=0.035). However, having personal experience with breastfeeding (self or partner) did not increased breastfeeding attitudes and knowledge (p=0.35 vs. p=0.93, respectively).Conclusions: Medical students have significant educational needs in the area of breastfeeding management and breastfeeding education. Further targeted training is needed to improve both breastfeeding attitudes and knowledge
[Letter from P. A. Wood to Barbara Jordan - December 6, 1977]
No full textLetter from Mrs. P. A. Woods to Barbara Jordan discussing Jordan's decision to not run for re-election and how much she will be missed
Structure of Chlorobium vibrioforme 5-aminolaevulinic acid dehydratase complexed with a diacid inhibitor
No full textThe structure of Chlorobium vibrioforme 5-aminolaevulinic acid dehydratase (ALAD) complexed with the irreversible inhibitor 4,7-dioxosebacic acid has been solved. The inhibitor binds by forming Schiff-base linkages with lysines 200 and 253 at the active site. The structure reported here provides a definition of the interactions made by both of the substrate molecules (A-side and P-side substrates) with the C. vibrioforme ALAD and is compared and contrasted with structures of the same inhibitor bound to Escherichia coli and yeast ALAD. The structure suggests why 4,7-dioxosebacic acid is a better inhibitor of the zinc-dependent ALADs than of the zinc-independent ALADs
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