The Experts below are selected from a list of 54 Experts worldwide ranked by ideXlab platform
Hilary J. Powers - One of the best experts on this subject based on the ideXlab platform.
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Erythrocyte Pyridoxamine Phosphate Oxidase activity: a potential biomarker of riboflavin status?
The American journal of clinical nutrition, 2009Co-Authors: Sohail Mushtaq, Marilyn H. Hill, Hilary J. PowersAbstract:Background: Riboflavin status is commonly measured by the in vitro stimulation of erythrocyte glutathione reductase with flavin adenine dinucleotide (FAD) and expressed as an erythrocyte glutathione reductase activation coefficient (EGRAC). However, this assay is insensitive to poor riboflavin status in subjects with glucose-6Phosphate dehydrogenase (G6PD) deficiency. Because G6PD deficiency is common in parts of the world where ariboflavinosis is endemic, it is important to have a measure of riboflavin status that is unaffected by differences in G6PD status. Objective: The objective was to further develop and validate a fluorometric assay for Pyridoxamine Phosphate Oxidase (PPO) activity as a measure of riboflavin status. Design: A fluorometric assay was optimized for the flavin-dependent enzyme PPO in erythrocytes. Hemolysates from a previous riboflavin intervention study (2- and 4-mg riboflavin supplements) were used to investigate the responsiveness of the method to changes in riboflavin intake. Results: PPO activity and the PPO activation coefficient (PPOAC) were used to assess riboflavin status. Both PPO activity and PPOAC responded to riboflavin supplements (P , 0.01), but only PPO showed a dose response (P , 0.001). The change from baseline to after the intervention in PPOAC and PPO enzyme activity was significantly inversely correlated (P , 0.001). Both PPO activity and PPOAC were strongly correlated with EGRAC (P , 0.001). Additionally, both PPOAC and EGRAC showed a significant inverse correlation with dietary riboflavin intake (P , 0.01); PPO activity was positively correlated with riboflavin intake (P , 0.01). Conclusions: PPO activity could be used as a biomarker for measuring riboflavin status, especially in populations with a high prevalence of G6PD deficiency. This trial is registered at www.isrctn. org as ISRCTN35811298. Am J Clin Nutr doi: 10.3945/
Emile Van Schaftingen - One of the best experts on this subject based on the ideXlab platform.
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Pyridoxamine-Phosphate Oxidases and Pyridoxamine-Phosphate Oxidase-related proteins catalyze the oxidation of 6-NAD(P)H to NAD(P).
The Biochemical journal, 2019Co-Authors: Alexandre Marbaix, Georges Chehade, Gaëtane Noël, Pierre Morsomme, Didier Vertommen, Guido T. Bommer, Emile Van SchaftingenAbstract:6-NADH and 6-NADPH are strong inhibitors of several dehydrogenases that may form spontaneously from NAD(P)H. They are known to be oxidized to NAD(P)+ by mammalian renalase, an FAD-linked enzyme mainly present in heart and kidney, and by related bacterial enzymes. We partially purified an enzyme oxidizing 6-NADPH from rat liver, and, surprisingly, identified it as Pyridoxamine-Phosphate Oxidase (PNPO). This was confirmed by the finding that recombinant mouse PNPO oxidized 6-NADH and 6-NADPH with catalytic efficiencies comparable to those observed with pyridoxine- and Pyridoxamine-5'-Phosphate. PNPOs from Escherichia coli, Saccharomyces cerevisiae and Arabidopsis thaliana also displayed 6-NAD(P)H Oxidase activity, indicating that this 'side-activity' is conserved. Remarkably, 'Pyridoxamine-Phosphate Oxidase-related proteins' (PNPO-RP) from Nostoc punctiforme, A. thaliana and the yeast S. cerevisiae (Ygr017w) were not detectably active on pyridox(am)ine-5'-P, but oxidized 6-NADH, 6-NADPH and 2-NADH suggesting that this may be their main catalytic function. Their specificity profiles were therefore similar to that of renalase. Inactivation of renalase and of PNPO in mammalian cells and of Ygr017w in yeasts led to the accumulation of a reduced form of 6-NADH, tentatively identified as 4,5,6-NADH3, which can also be produced in vitro by reduction of 6-NADH by glyceraldehyde-3-Phosphate dehydrogenase or glucose-6-Phosphate dehydrogenase. As 4,5,6-NADH3 is not a substrate for renalase, PNPO or PNPO-RP, its accumulation presumably reflects the block in the oxidation of 6-NADH. These findings indicate that two different classes of enzymes using either FAD (renalase) or FMN (PNPOs and PNPO-RPs) as a cofactor play an as yet unsuspected role in removing damaged forms of NAD(P).
Sohail Mushtaq - One of the best experts on this subject based on the ideXlab platform.
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Erythrocyte Pyridoxamine Phosphate Oxidase activity: a potential biomarker of riboflavin status?
The American journal of clinical nutrition, 2009Co-Authors: Sohail Mushtaq, Marilyn H. Hill, Hilary J. PowersAbstract:Background: Riboflavin status is commonly measured by the in vitro stimulation of erythrocyte glutathione reductase with flavin adenine dinucleotide (FAD) and expressed as an erythrocyte glutathione reductase activation coefficient (EGRAC). However, this assay is insensitive to poor riboflavin status in subjects with glucose-6Phosphate dehydrogenase (G6PD) deficiency. Because G6PD deficiency is common in parts of the world where ariboflavinosis is endemic, it is important to have a measure of riboflavin status that is unaffected by differences in G6PD status. Objective: The objective was to further develop and validate a fluorometric assay for Pyridoxamine Phosphate Oxidase (PPO) activity as a measure of riboflavin status. Design: A fluorometric assay was optimized for the flavin-dependent enzyme PPO in erythrocytes. Hemolysates from a previous riboflavin intervention study (2- and 4-mg riboflavin supplements) were used to investigate the responsiveness of the method to changes in riboflavin intake. Results: PPO activity and the PPO activation coefficient (PPOAC) were used to assess riboflavin status. Both PPO activity and PPOAC responded to riboflavin supplements (P , 0.01), but only PPO showed a dose response (P , 0.001). The change from baseline to after the intervention in PPOAC and PPO enzyme activity was significantly inversely correlated (P , 0.001). Both PPO activity and PPOAC were strongly correlated with EGRAC (P , 0.001). Additionally, both PPOAC and EGRAC showed a significant inverse correlation with dietary riboflavin intake (P , 0.01); PPO activity was positively correlated with riboflavin intake (P , 0.01). Conclusions: PPO activity could be used as a biomarker for measuring riboflavin status, especially in populations with a high prevalence of G6PD deficiency. This trial is registered at www.isrctn. org as ISRCTN35811298. Am J Clin Nutr doi: 10.3945/
S J Pethybridge - One of the best experts on this subject based on the ideXlab platform.
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mating type gene structure and spatial distribution of didymella tanaceti in pyrethrum fields
Phytopathology, 2016Co-Authors: Tamieka L Pearce, J B Scott, F S Hay, S J PethybridgeAbstract:Tan spot of pyrethrum (Tanacetum cinerariifolium) is caused by the ascomycete Didymella tanaceti. To assess the evolutionary role of ascospores in the assumed asexual species, the structure and arrangement of mating-type (MAT) genes were examined. A single MAT1-1 or MAT1-2 idiomorph was identified in all isolates examined, indicating that the species is heterothallic. The idiomorphs were flanked upstream and downstream by regions encoding Pyridoxamine Phosphate Oxidase-like and DNA lyase-like proteins, respectively. A multiplex MAT-specific polymerase chain reaction assay was developed and used to genotype 325 isolates collected within two transects in each of four fields in Tasmania, Australia. The ratio of isolates of each mating-type in each transect was consistent with a 1:1 ratio. The spatial distribution of the isolates of the two mating-types within each transect was random for all except one transect for MAT1-1 isolates, indicating that clonal patterns of each mating-type were absent. However, evidence of a reduced selection pressure on MAT1-1 isolates was observed, with a second haplotype of the MAT1-1-1 gene identified in 4.4% of MAT1-1 isolates. In vitro crosses between isolates with opposite mating-types failed to produce ascospores. Although the sexual morph could not be induced, the occurrence of both mating-types in equal frequencies suggested that a cryptic sexual mode of reproduction may occur within field populations.
Michel Guilloton - One of the best experts on this subject based on the ideXlab platform.
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Sterol uptake induced by an impairment of pyridoxal Phosphate synthesis in Saccharomyces cerevisiae: cloning and sequencing of the PDX3 gene encoding pyridoxine (Pyridoxamine) Phosphate Oxidase.
Journal of bacteriology, 1995Co-Authors: Adil Loubbardi, Christophe Marcireau, Francis Karst, Michel GuillotonAbstract:Exogenous sterols do not permeate wild-type Saccharomyces cerevisiae in aerobic conditions. However, mutant strain FKerg7, affected in lanosterol synthase, is a sterol auxotroph which is able to grow aerobically in the presence of ergosterol. Viability of this strain depends on the presence of an additional mutation, aux30, that leads to sterol permeability. Cells bearing the aux30 mutation fail to grow in standard yeast nitrogen base medium containing pyridoxine but grow normally if pyridoxine is replaced by either pyridoxal or Pyridoxamine. These mutants are characterized by a lack in pyridoxine (Pyridoxamine) Phosphate Oxidase [P(N/M)P Oxidase] (EC 1.4.3.5) activity. The pleiotropic phenotype induced by the aux30 mutation includes a strong perturbation in amino acid biosynthesis. Strains bearing the aux30 mutation also display atypic fatty acid, sterol, and cytochrome patterns. Transformation of an aux30 strain with a replicative vector carrying the wild-type PDX3 gene encoding P(N/M)P Oxidase restored wild-type fatty acid, sterol, and cytochrome patterns and suppressed exogenous sterol accumulation. It is proposed that sterol permeation of aux30 strains in mainly the consequence of their leaky Hem- character. The amino acid sequence of S. cerevisiae P(N/M)P Oxidase inferred from the nucleotide sequence of PDX3 shows a high percentage of homology with the corresponding enzymes from Escherichia coli and Myxococcus xanthus. Several putative Gcn4p binding sequences are present in the PDX3 promoter region, leading to the assumption that transcription of this gene is under the general control of nitrogen metabolism.
