The Experts below are selected from a list of 1549824 Experts worldwide ranked by ideXlab platform
Jennifer Bridwellrabb - One of the best experts on this subject based on the ideXlab platform.
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aerobic Enzymes and their radical sam Enzyme counterparts in tetrapyrrole pathways
Biochemistry, 2019Co-Authors: Jennifer BridwellrabbAbstract:Microorganisms have lifestyles and metabolism adapted to environmental niches, which can be very broad or highly restricted. Molecular oxygen (O2) is currently variably present in microenvironments and has driven adaptation and microbial differentiation over the course of evolution on Earth. Obligate anaerobes use Enzymes and cofactors susceptible to low levels of O2 and are restricted to O2-free environments, whereas aerobes typically take advantage of O2 as a reactant in many biochemical pathways and may require O2 for essential biochemical reactions. In this Perspective, we focus on analogous Enzymes found in tetrapyrrole biosynthesis, modification, and degradation that are catalyzed by O2-sensitive radical S-adenosylmethionine (SAM) Enzymes and by O2-dependent metalloEnzymes. We showcase four transformations for which aerobic organisms use O2 as a cosubstrate but anaerobic organisms do not. These reactions include oxidative decarboxylation, methyl and methylene oxidation, ring formation, and ring clea...
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aerobic Enzymes and their radical sam Enzyme counterparts in tetrapyrrole pathways
Biochemistry, 2019Co-Authors: Jennifer BridwellrabbAbstract:Microorganisms have lifestyles and metabolism adapted to environmental niches, which can be very broad or highly restricted. Molecular oxygen (O2) is currently variably present in microenvironments...
Joan B Broderick - One of the best experts on this subject based on the ideXlab platform.
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mechanistic studies of radical sam Enzymes pyruvate formate lyase activating Enzyme and lysine 2 3 aminomutase case studies
Methods in Enzymology, 2018Co-Authors: Amanda S Byer, William E Broderick, Elizabeth C Mcdaniel, Stella Impano, Joan B BroderickAbstract:Abstract The radical SAM Enzyme superfamily is large and diverse, with ever-increasing numbers of examples of characterized reactions. This chapter focuses on the methodology we have developed over the last 25 years for working with these Enzymes, with the specific examples discussed being the pyruvate formate-lyase activating Enzyme (PFL-AE) and lysine 2,3-aminomutase (LAM). Both Enzymes are purified from overexpressing Escherichia coli, but differ in that PFL-AE is expressed without an affinity tag and does not require iron–sulfur cluster reconstitution, while LAM purification is carried out through use of a His6 affinity tag and the Enzyme benefits from cluster reconstitution. Because of radical SAM Enzymes’ catalytic need for a [4Fe–4S] cluster, we present methods for characterization and incorporation of a full [4Fe–4S] cluster in addition to Enzyme activity assay protocols. Synthesis of SAM (S-adenosyl- l -methionine) and its analogs have played an important role in our mechanistic studies of radical SAM Enzymes, and their synthetic methods are also presented in detail.
Matthias Schwab - One of the best experts on this subject based on the ideXlab platform.
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cytochrome p450 Enzymes in drug metabolism regulation of gene expression Enzyme activities and impact of genetic variation
Pharmacology & Therapeutics, 2013Co-Authors: Ulrich M Zanger, Matthias SchwabAbstract:Cytochromes P450 (CYP) are a major source of variability in drug pharmacokinetics and response. Of 57 putatively functional human CYPs only about a dozen Enzymes, belonging to the CYP1, 2, and 3 families, are responsible for the biotransformation of most foreign substances including 70-80% of all drugs in clinical use. The highest expressed forms in liver are CYPs 3A4, 2C9, 2C8, 2E1, and 1A2, while 2A6, 2D6, 2B6, 2C19 and 3A5 are less abundant and CYPs 2J2, 1A1, and 1B1 are mainly expressed extrahepatically. Expression of each CYP is influenced by a unique combination of mechanisms and factors including genetic polymorphisms, induction by xenobiotics, regulation by cytokines, hormones and during disease states, as well as sex, age, and others. Multiallelic genetic polymorphisms, which strongly depend on ethnicity, play a major role for the function of CYPs 2D6, 2C19, 2C9, 2B6, 3A5 and 2A6, and lead to distinct pharmacogenetic phenotypes termed as poor, intermediate, extensive, and ultrarapid metabolizers. For these CYPs, the evidence for clinical significance regarding adverse drug reactions (ADRs), drug efficacy and dose requirement is rapidly growing. Polymorphisms in CYPs 1A1, 1A2, 2C8, 2E1, 2J2, and 3A4 are generally less predictive, but new data on CYP3A4 show that predictive variants exist and that additional variants in regulatory genes or in NADPH:cytochrome P450 oxidoreductase (POR) can have an influence. Here we review the recent progress on drug metabolism activity profiles, interindividual variability and regulation of expression, and the functional and clinical impact of genetic variation in drug metabolizing P450s.
Cheryl A Kerfeld - One of the best experts on this subject based on the ideXlab platform.
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In Vitro Characterization and Concerted Function of Three Core Enzymes of a Glycyl Radical Enzyme - Associated Bacterial Microcompartment
Scientific Reports, 2017Co-Authors: Jan Zarzycki, Niña Socorro Cortina, Markus Sutter, Cheryl A KerfeldAbstract:Many bacteria encode proteinaceous bacterial microcompartments (BMCs) that encapsulate sequential enzymatic reactions of diverse metabolic pathways. Well-characterized BMCs include carboxysomes for CO_2-fixation, and propanediol- and ethanolamine-utilizing microcompartments that contain B_12-dependent Enzymes. Genes required to form BMCs are typically organized in gene clusters, which promoted their distribution across phyla by horizontal gene transfer. Recently, BMCs associated with glycyl radical Enzymes (GREs) were discovered; these are widespread and comprise at least three functionally distinct types. Previously, we predicted one type of these GRE-associated microcompartments (GRMs) represents a B_12-independent propanediol-utilizing BMC. Here we functionally and structurally characterize Enzymes of the GRM of Rhodopseudomonas palustris BisB18 and demonstrate their concerted function in vitro . The GRM signature Enzyme, the GRE, is a dedicated 1,2-propanediol dehydratase with a new type of intramolecular encapsulation peptide. It forms a complex with its activating Enzyme and, in conjunction with an aldehyde dehydrogenase, converts 1,2-propanediol to propionyl-CoA. Notably, homologous GRMs are also encoded in pathogenic Escherichia coli strains. Our high-resolution crystal structures of the aldehyde dehydrogenase lead to a revised reaction mechanism. The successful in vitro reconstitution of a part of the GRM metabolism provides insights into the metabolic function and steps in the assembly of this BMC.
Rachel F Tyndale - One of the best experts on this subject based on the ideXlab platform.
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Brain Drug-Metabolizing Cytochrome P450 Enzymes are Active In Vivo, Demonstrated by Mechanism-Based Enzyme Inhibition
Neuropsychopharmacology, 2009Co-Authors: Sharon Miksys, Rachel F TyndaleAbstract:Individuals vary in their response to centrally acting drugs, and this is not always predicted by drug plasma levels. Central metabolism by brain cytochromes P450 (CYPs) may contribute to interindividual variation in response to drugs. Brain CYPs have unique regional and cell-type expression and induction patterns, and they are regulated independently of their hepatic isoforms. In vitro , these Enzymes can metabolize endogenous and xenobiotic substrates including centrally acting drugs, but there is no evidence to date of their in vivo function. This has been difficult to demonstrate in the presence of hepatically derived metabolites that may cross the blood–brain barrier. In addition, because of the membrane location of brain CYPs and the rate limiting effect of endogenous heme levels on the activity and appropriate membrane insertion of some induced CYPs, it has been unclear whether sufficient cofactors and coEnzymes are present for constitutive and induced CYP forms to be enzymatically active. We have developed a method using a radiolabeled mechanism-based inhibitor of CYP2B1, ^3H-8-methoxypsoralen, to demonstrate for the first time that both the constitutive and induced forms of this Enzyme are active in situ in the living rat brain. This methodology provides a novel approach to assess the function of Enzymes in extrahepatic tissues, where expression levels are often low. Selective induction of metabolically active drug metabolizing Enzymes in the brain may also provide ways to control prodrug activation in specific brain regions as a novel therapeutic avenue.
