Characterization of human platelet glutathione reductase.
Glutathione reductase (NAD(P)h:oxidized glutathione oxidoreductase, EC 1.6.4.2) has been purified 1000-fold from the cytoplasmic fraction of human platelets. Salts, including the heretofore unreported effect of sodium citrate, activate the NADPH-dependent reduction of oxidized glutathione. Sodium citrate and monovalent salt activation appears to involve multiple sites having different binding affinities. At sub-saturating sodium phosphate, non-linear double reciprocal plots indicative of substrate activation by oxidized glutathione were observed. Initial velocity double reciprocal plots at sub-saturating and saturating concentrations of phosphate generate a family of converging lines. NADP+ is a partial inhibitor, indicating that the reduction of oxidized glutathione can proceed by more than one pathway. FMN, FAD, and riboflavin inhibit platelet glutathione reductase by influencing only the V while nitrofurantoin inhibition is associated with an increase Koxidized glutathione and a decreased V.
D001665:Binding Sites; D001792:Blood Platelets / Q000201:enzymology*; D003593:Cytoplasm / Q000201:enzymology; D004789:Enzyme Activation; D005415:Flavins / Q000494:pharmacology; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000097:blood* / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D009249:NADP / Q000494:pharmacology; D009582:Nitrofurantoin / Q000494:pharmacology; D010084:Oxidation-Reduction
D005415:Flavins; D009249:NADP; D009582:Nitrofurantoin; D005980:Glutathione Reductase