Properties of NADH-cytochrome-b5 reductase from human neutrophils.
An NADH-ferricyanide reductase activity of ca. 170 nmole ferricyanide reduced/min/10(7) cells is present in the membrane fraction of human neutrophils. This membrane-bound activity constitutes ca. 85% of the total NADH-ferricyanide reductase activity that is present in these cells. The enzyme(s) readily utilize(s) purified cytochrome-b5 from beef liver as an electron acceptor. No other physiologic electron acceptors tested (e.g., ubiquinone-30, menadione) were active. The specificities of electron donors (e.g., NADH congruent to deamino-NADH much greater than NADPH) and acceptors (e.g., Fe(CN)6-3 greater than 2,6-dichlorophenol-indophenol much greater than O2) for the enzyme(s) in unfractionated membranes, along with action of inhibitors (e.g., ADP, p-chloromercuribenzoate) and the pH optimum, indicate that virtually all of the membrane-bound ferricyanide reductase activity in these cells is NADH-cytochrome-b5 reductase. This reductase, however, is only slightly solubilized (ca. 10%) by a phosphate buffer extraction procedure that is effective with the liver enzyme.
D000227:Adenine Nucleotides / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002614:Chelating Agents / Q000494:pharmacology; D003579:Cytochrome Reductases / Q000378:metabolism*; D042966:Cytochrome-B(5) Reductase; D003864:Depression, Chemical; D003902:Detergents / Q000494:pharmacology; D005292:Ferricyanides / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009504:Neutrophils / Q000201:enzymology*; D013268:Stimulation, Chemical; D013379:Substrate Specificity
D000227:Adenine Nucleotides; D002614:Chelating Agents; D003902:Detergents; D005292:Ferricyanides; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase