Activation of the human neutrophil NADPH oxidase results in coupling of electron carrier function between ubiquinone-10 and cytochrome b559.
The enzymatic activity underlying the respiratory burst in human neutrophils was examined in a subcellular fraction with high specific activity and shown to be a membrane-associated complex of a flavoprotein, ubiquinone-10, and cytochrome b559 in an approximate 1.3:1:2 molar ratio. Study of the redox poise of these electron carriers indicated that electron flow in the intact complex from unstimulated cells proceeded: NADPH----E-FAD----ubiquinone-10. Similar studies on the complex prepared from stimulated neutrophils indicated that electron flow proceeded: NADPH----E-FAD----ubiquinone-10----cytochrome b559----oxygen. The active enzyme complex was inhibited by p-chloromercuribenzoate. Inhibition persisted after removal of excess inhibitor, was reversed by dithiothreitol, and could be blocked by prior addition of substrate (NADPH). Inhibition of the active oxidase complex by p-chloromercuribenzoate also inhibited electron flow from NADPH to all purported electron carriers in the chain (i.e. E-FAD, ubiquinone-10, and cytochrome b559). We conclude that activation of the oxidase enzyme complex in the intact neutrophil resulted in linkage of electron carrier function between endogenous ubiquinone-10 and cytochrome b559 and was without demonstrable effect on proximal electron flow. The p-chloromercuribenzoate sensitive site(s) proximal to the initial electron acceptor (E-FAD) did not appear to be altered by the cellular activation process.
Gabig
T G
TG
Lefker
B A
BA
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003573:Cytochrome b Group / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology*; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex; D014451:Ubiquinone / Q000378:metabolism*
D003573:Cytochrome b Group; D045332:Photosystem II Protein Complex; D014451:Ubiquinone; D002731:4-Chloromercuribenzenesulfonate; C019313:cytochrome b559; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C025204:Ubiquinone Q2; D004229:Dithiothreitol