Studies on the electron-transfer mechanism of the human neutrophil NADPH oxidase.
A superoxide-generating NADPH oxidase was solubilized from phorbol 12-myristate 13-acetate-activated human neutrophils with a mixture of sodium deoxycholate (0.125%, w/v) and Lubrol-PX (0.125%, v/v). The solubilized preparation contained FAD (577 pmol/mg of protein) and cytochrome b-245 (479 pmol/mg of protein) and produced 11.61 mol of O2-./s per mol of cytochrome b (340 nmol of O2-./min per mg of protein). On addition of NADPH, the cytochrome b-245 was reduced by 7.9% and the FAD by 38% in the aerobic steady state; NADH addition caused little steady-state reduction of cytochrome b and FAD. In this preparation, and several others, the measured rate of O2-. production correlated with the turnover of cytochrome b calculated from the extent of cytochrome b-245 reduction under aerobic conditions. Addition of diphenyleneiodonium abolished the reduction of both the FAD and cytochrome b-245 components and inhibited O2-. production. The haem ligand imidazole inhibited O2-. generation and cytochrome b reduction while permitting FAD reduction. These results support the suggestion that the human neutrophil NADPH oxidase has the electron-transport sequence: NADPH----FAD----cytochrome b-245----O2.
Ellis
J A
JA
Department of Biochemistry, Medical School, University of Bristol, U.K.
Cross
A R
AR
Jones
O T
OT
D003573:Cytochrome b Group / Q000097:blood; D004579:Electron Transport; D005182:Flavin-Adenine Dinucleotide / Q000097:blood; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000097:blood*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D012995:Solubility; D013481:Superoxides / Q000097:blood
D003573:Cytochrome b Group; C035130:cytochrome b245; D013481:Superoxides; D005182:Flavin-Adenine Dinucleotide; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases