The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform
Chandrakant Bonde - One of the best experts on this subject based on the ideXlab platform.
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Decaprenyl-phosphoryl-ribose 2'-epimerase (DprE1): challenging target for antitubercular drug discovery.
Chemistry Central Journal, 2018Co-Authors: Jineetkumar Gawad, Chandrakant BondeAbstract:Tuberculosis has proved harmful to the entire history of mankind from past several decades. Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1) is a recent target which was identified in 2009 but unfortunately it is neither explored nor crossed phase II. In past several decades few targets were identified for effective antitubercular drug discovery. Resistance is the major problem for effective antitubercular drug discovery. Arabinose is constituent of mycobacterium cell wall. Biosynthesis of arabinose is FAD dependant two step epimerisation reaction which is catalysed by DprE1 and DprE2 Flavoprotein Enzymes. The current review is mainly emphases on DprE1 as a perspective challenge for further research.
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Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1): challenging target for antitubercular drug discovery
Chemistry Central Journal, 2018Co-Authors: Jineetkumar Gawad, Chandrakant BondeAbstract:Tuberculosis has proved harmful to the entire history of mankind from past several decades. Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1) is a recent target which was identified in 2009 but unfortunately it is neither explored nor crossed phase II. In past several decades few targets were identified for effective antitubercular drug discovery. Resistance is the major problem for effective antitubercular drug discovery. Arabinose is constituent of mycobacterium cell wall. Biosynthesis of arabinose is FAD dependant two step epimerisation reaction which is catalysed by DprE1 and DprE2 Flavoprotein Enzymes. The current review is mainly emphases on DprE1 as a perspective challenge for further research.
Jineetkumar Gawad - One of the best experts on this subject based on the ideXlab platform.
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Decaprenyl-phosphoryl-ribose 2'-epimerase (DprE1): challenging target for antitubercular drug discovery.
Chemistry Central Journal, 2018Co-Authors: Jineetkumar Gawad, Chandrakant BondeAbstract:Tuberculosis has proved harmful to the entire history of mankind from past several decades. Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1) is a recent target which was identified in 2009 but unfortunately it is neither explored nor crossed phase II. In past several decades few targets were identified for effective antitubercular drug discovery. Resistance is the major problem for effective antitubercular drug discovery. Arabinose is constituent of mycobacterium cell wall. Biosynthesis of arabinose is FAD dependant two step epimerisation reaction which is catalysed by DprE1 and DprE2 Flavoprotein Enzymes. The current review is mainly emphases on DprE1 as a perspective challenge for further research.
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Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1): challenging target for antitubercular drug discovery
Chemistry Central Journal, 2018Co-Authors: Jineetkumar Gawad, Chandrakant BondeAbstract:Tuberculosis has proved harmful to the entire history of mankind from past several decades. Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1) is a recent target which was identified in 2009 but unfortunately it is neither explored nor crossed phase II. In past several decades few targets were identified for effective antitubercular drug discovery. Resistance is the major problem for effective antitubercular drug discovery. Arabinose is constituent of mycobacterium cell wall. Biosynthesis of arabinose is FAD dependant two step epimerisation reaction which is catalysed by DprE1 and DprE2 Flavoprotein Enzymes. The current review is mainly emphases on DprE1 as a perspective challenge for further research.
Nigel S. Scrutton - One of the best experts on this subject based on the ideXlab platform.
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Practical aspects on the use of kinetic isotope effects as probes of Flavoprotein enzyme mechanisms.
Methods in molecular biology (Clifton N.J.), 2014Co-Authors: Christopher R. Pudney, Sam Hay, Nigel S. ScruttonAbstract:The measurement of kinetic isotope effects (KIEs) has proved useful in many mechanistic studies of enzyme activity, most notably in enzyme-catalyzed hydrogen-transfer reactions. Primary KIEs (1° KIE) greater than unity indicate that transfer of the hydrogen species of interest is partially or fully rate limiting, and studies of the magnitude of the temperature and pressure dependence of these KIEs can inform on the mechanism of transfer. For example, KIE measurements have proved crucial in understanding the role of quantum mechanical tunneling in enzyme systems. The measurement of secondary KIEs (2° KIEs) is also informative and can be used to infer a significant tunneling contribution and details of transition state geometry. Here the deuterium label is introduced next to that of the transferred hydrogen. Measurements of 1° and 2° KIEs are being used increasingly in studies of H-transfer in Flavoprotein Enzymes and this requires the preparation of high purity and stereospecific labeled isotopologues. Strategies for the synthesis of labeled substrates are dependent on the enzyme system being studied. However, the nicotinamide coEnzymes are often used in studies of Flavoprotein enzyme mechanisms. Here, we provide practical details for the enzymatic synthesis of high purity deuterated isotopologues of the common biological coEnzymes NADH and NADPH as well as the corresponding nonreactive mimics, tetrahydroNAD(P)H. Both forms of the coenzyme have proven useful in the study of mechanisms, particularly in relation to the involvement of quantum mechanical tunneling and dynamics in enzymatic H-transfer chemistry. The focus here is on practical considerations in the synthesis of these compounds. We also provide an abbreviated description of how measurements of KIEs can inform on Flavoprotein mechanisms. The aim of this contribution is not to give a detailed description of the underlying theory (which has been reviewed extensively in the literature), but to provide a basic introduction and practical considerations for nonexpert readers who wish to incorporate such measurements in studies of enzyme mechanisms.
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The Human Apoptosis-inducing Protein AMID Is an Oxidoreductase with a Modified Flavin Cofactor and DNA Binding Activity
The Journal of biological chemistry, 2005Co-Authors: Ker R. Marshall, Nigel S. Scrutton, Min Gong, Leigh Wodke, John H. Lamb, Donald J. L. Jones, Peter B. Farmer, Andrew W. MunroAbstract:Abstract AMID (apoptosis-inducing factor-homologous mitochondrion-associated inducer of death; also known as PRG3 (p53-responsive gene 3)) is a human caspase-independent pro-apoptotic protein with some similarity to apoptosis-inducing factor. AMID was purified from a recombinant bacterial host, enabling biochemical analysis of the protein. AMID is a Flavoprotein; possesses NAD(P)H oxidase activity; and catalyzes NAD(P)H-dependent reduction of cytochrome c and other electron acceptors, including molecular oxygen. NADPH binds ∼10-fold tighter than NADH. AMID binds 6-hydroxy-FAD (a cofactor that accumulates only adventitiously and at low abundance in other Flavoprotein Enzymes) to form a stoichiometric cofactor·protein complex. AMID has a distinctive electronic spectrum due to the modified flavin. NAD(P)+ binding perturbed the spectrum, enabling determination of Kd values for these coEnzymes. 6-Hydroxy-FAD could be removed from AMID and the apoprotein reconstituted with FAD. FAD was converted to 6-hydroxy-FAD in reconstituted AMID during aerobic turnover with NADPH. AMID is a DNA-binding protein that lacks apparent DNA sequence specificity. Formation of the protein·DNA complex (i) effected a major protein conformational change and (ii) was prevented in the presence of nicotinamide coenzyme. Apo-AMID retains DNA binding activity. Our studies establish a link between coenzyme and DNA binding that likely impacts on the physiological role of AMID in cellular apoptosis.
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Chemical aspects of amine oxidation by Flavoprotein Enzymes
Natural product reports, 2004Co-Authors: Nigel S. ScruttonAbstract:Covering: 1980–September 2004 The mechanism of amine oxidation by Flavoprotein Enzymes is critically analysed through analysis of available experimental data. The review assesses available evidence for radical and polar mechanisms, drawing on data from model reactions, kinetic and spectroscopic approaches, structural and mutagenesis studies. The review focuses on studies of mammalian monoamine oxidases and the bacterial Enzymes trimethylamine dehydrogenase, monomeric sarcosine oxidase and dimethylglycine oxidase.
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Effects of environment on flavin reactivity in morphinone reductase: analysis of Enzymes displaying differential charge near the N-1 atom and C-2 carbonyl region of the active-site flavin
Biochemical Journal, 2001Co-Authors: Daniel H. Craig, Andrew W. Munro, Terez Barna, Peter C. E. Moody, Neil C. Bruce, Stephen K. Chapman, Nigel S. ScruttonAbstract:The side chain of residue Arg238 in morphinone reductase (MR) is located close to the N-1/C-2 carbonyl region of the flavin isoalloxazine ring. During enzyme reduction negative charge develops in this region of the flavin. The positioning of a positively charged side chain in the N-1/C-2 carbonyl region of protein-bound flavin is common to many Flavoprotein Enzymes. To assess the contribution made by Arg238 in stabilizing the reduced flavin in MR we isolated three mutant forms of the enzyme in which the position of the positively charged side chain was retracted from the N-1/C-2 carbonyl region (Arg238 → Lys), the positive charge was removed (Arg238 → Met) or the charge was reversed (Arg238 → Glu). Each mutant enzyme retains flavin in its active site. Potentiometric studies of the flavin in the wild-type and mutant forms of MR indicate that the flavin semiquinone is not populated to any appreciable extent. Reduction of the flavin in each enzyme is best described by a single Nernst function, and the values of the midpoint reduction potentials (E12) for each enzyme fall within the region of −247±10mV. Stopped-flow studies of NADH binding to wild-type and mutant MR Enzymes reveal differences in the kinetics of formation and decay of an enzyme–NADH charge-transfer complex, reflecting small perturbations in active-site geometry. Reduced rates of hydride transfer in the mutant Enzymes are attributed to altered geometrical alignment of the nicotinamide coenzyme with FMN rather than major perturbations in reduction potential, and this is supported by an observed entropy–enthalpy compensation effect on the hydride transfer reaction throughout the series of Enzymes. The data indicate, in contrast with dogma, that the presence of a positively charged side chain close to the N-1/C-2 carbonyl region of the flavin in MR is not required to stabilize the reduced flavin. This finding may have general implications for flavoenzyme catalysis, since it has generally been assumed that positive charge in this region has a stabilizing effect on the reduced form of flavin.
Vincent Massey - One of the best experts on this subject based on the ideXlab platform.
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Reaction of reduced flavins and Flavoproteins with diphenyliodonium chloride.
The Journal of biological chemistry, 2002Co-Authors: Sumita Chakraborty, Vincent MasseyAbstract:The reaction of diphenyliodonium chloride with free reduced flavins has been studied by stopped flow spectrophotometry under anaerobic conditions, and second order rate constants were determined as a function of pH. The reactive flavin species was identified as the reduced anion, based on an observed reaction pK of 6.7. The product mixture was independent of the initial concentration of reactant and contained approximately 20% oxidized flavin. The results can be modeled quantitatively on a modification of the mechanism proposed by Tew (Tew, D. G. (1993) Biochemistry 32, 10209-10215). The composition of the complex reaction mixture has been analyzed, and four flavin-phenyl adducts with distinctive absorbance and fluorescence characteristics have been identified, involving substitution at the flavin C4a, N5, and C8 positions. Inactivation of Flavoprotein Enzymes by diphenyliodonium has also been studied, and several examples were found where inactivation occurs readily, despite noninvolvement of radical intermediates in their reaction mechanisms. It can be concluded that inactivation by phenyliodonium species is not a valid indicator of catalytic mechanism involving radical intermediates. One of the several factors determining inactivation is maintenance of the enzyme flavin in the reduced form in the steady state of catalysis, the other factors being redox potential and accessibility of the inhibitor to the flavin active site.
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the chemical and biological versatility of riboflavin
Biochemical Society Transactions, 2000Co-Authors: Vincent MasseyAbstract:Since their discovery and chemical characterization in the 1930s, flavins have been recognized as being capable of both one- and two-electron transfer processes, and as playing a pivotal role in coupling the two-electron oxidation of most organic substrates to the one-electron transfers of the respiratory chain. In addition, they are now known as versatile compounds that can function as electrophiles and nucleophiles, with covalent intermediates of flavin and substrate frequently being involved in catalysis. Flavins are thought to contribute to oxidative stress through their ability to produce superoxide, but at the same time flavins are frequently involved in the reduction of hydroperoxides, products of oxygen-derived radical reactions. Flavoproteins play an important role in soil detoxification processes via the hydroxylation of many aromatic compounds, and a simple Flavoprotein in liver microsomes catalyses many reactions similar to those carried out by cytochrome P450 Enzymes. Flavins are involved in the production of light in bioluminescent bacteria, and are intimately connected with light-initiated reactions such as plant phototropism and nucleic acid repair processes. Recent reports also link them to programmed cell death. The chemical versatility of Flavoproteins is clearly controlled by specific interactions with the proteins with which they are bound. One of the main thrusts of current research is to try to define the nature of these interactions, and to understand in chemical terms the various steps involved in catalysis by Flavoprotein Enzymes.
Andrew W. Munro - One of the best experts on this subject based on the ideXlab platform.
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The Human Apoptosis-inducing Protein AMID Is an Oxidoreductase with a Modified Flavin Cofactor and DNA Binding Activity
The Journal of biological chemistry, 2005Co-Authors: Ker R. Marshall, Nigel S. Scrutton, Min Gong, Leigh Wodke, John H. Lamb, Donald J. L. Jones, Peter B. Farmer, Andrew W. MunroAbstract:Abstract AMID (apoptosis-inducing factor-homologous mitochondrion-associated inducer of death; also known as PRG3 (p53-responsive gene 3)) is a human caspase-independent pro-apoptotic protein with some similarity to apoptosis-inducing factor. AMID was purified from a recombinant bacterial host, enabling biochemical analysis of the protein. AMID is a Flavoprotein; possesses NAD(P)H oxidase activity; and catalyzes NAD(P)H-dependent reduction of cytochrome c and other electron acceptors, including molecular oxygen. NADPH binds ∼10-fold tighter than NADH. AMID binds 6-hydroxy-FAD (a cofactor that accumulates only adventitiously and at low abundance in other Flavoprotein Enzymes) to form a stoichiometric cofactor·protein complex. AMID has a distinctive electronic spectrum due to the modified flavin. NAD(P)+ binding perturbed the spectrum, enabling determination of Kd values for these coEnzymes. 6-Hydroxy-FAD could be removed from AMID and the apoprotein reconstituted with FAD. FAD was converted to 6-hydroxy-FAD in reconstituted AMID during aerobic turnover with NADPH. AMID is a DNA-binding protein that lacks apparent DNA sequence specificity. Formation of the protein·DNA complex (i) effected a major protein conformational change and (ii) was prevented in the presence of nicotinamide coenzyme. Apo-AMID retains DNA binding activity. Our studies establish a link between coenzyme and DNA binding that likely impacts on the physiological role of AMID in cellular apoptosis.
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Effects of environment on flavin reactivity in morphinone reductase: analysis of Enzymes displaying differential charge near the N-1 atom and C-2 carbonyl region of the active-site flavin
Biochemical Journal, 2001Co-Authors: Daniel H. Craig, Andrew W. Munro, Terez Barna, Peter C. E. Moody, Neil C. Bruce, Stephen K. Chapman, Nigel S. ScruttonAbstract:The side chain of residue Arg238 in morphinone reductase (MR) is located close to the N-1/C-2 carbonyl region of the flavin isoalloxazine ring. During enzyme reduction negative charge develops in this region of the flavin. The positioning of a positively charged side chain in the N-1/C-2 carbonyl region of protein-bound flavin is common to many Flavoprotein Enzymes. To assess the contribution made by Arg238 in stabilizing the reduced flavin in MR we isolated three mutant forms of the enzyme in which the position of the positively charged side chain was retracted from the N-1/C-2 carbonyl region (Arg238 → Lys), the positive charge was removed (Arg238 → Met) or the charge was reversed (Arg238 → Glu). Each mutant enzyme retains flavin in its active site. Potentiometric studies of the flavin in the wild-type and mutant forms of MR indicate that the flavin semiquinone is not populated to any appreciable extent. Reduction of the flavin in each enzyme is best described by a single Nernst function, and the values of the midpoint reduction potentials (E12) for each enzyme fall within the region of −247±10mV. Stopped-flow studies of NADH binding to wild-type and mutant MR Enzymes reveal differences in the kinetics of formation and decay of an enzyme–NADH charge-transfer complex, reflecting small perturbations in active-site geometry. Reduced rates of hydride transfer in the mutant Enzymes are attributed to altered geometrical alignment of the nicotinamide coenzyme with FMN rather than major perturbations in reduction potential, and this is supported by an observed entropy–enthalpy compensation effect on the hydride transfer reaction throughout the series of Enzymes. The data indicate, in contrast with dogma, that the presence of a positively charged side chain close to the N-1/C-2 carbonyl region of the flavin in MR is not required to stabilize the reduced flavin. This finding may have general implications for flavoenzyme catalysis, since it has generally been assumed that positive charge in this region has a stabilizing effect on the reduced form of flavin.