The particulate superoxide-forming system from human neutrophils. Properties of the system and further evidence supporting its participation in the respiratory burst.

Abstract

A B S T R A C T Studies were performed to characterize the previously reported particulate 02-forming system from human neutrophils. Of eight reducing agents ex- amined, including glutathione, ascorbic acid, and intermediates of the glycolytic and hexose monphosphate shunt pathways, only the pyridine nucleotides could serve as electron donors. At 0.1 mM pyridine nucleotide, 02production was relatively independent of pH. The Km for NADH was approximately 0.7 mM regardless of pH, while with NADPH the Km varied from 0.02 mM at pH 6.0 to 0.3 mM at pH 7.5. The molar ratio of NADPH oxidized to 02-produced was consistent with the reaction: NADPH + 2 02-NADP' + H+; the product nucleotide was shown enzymatically to be NADP. Oa2 production was not inhibited by CN-, N3-, EDTA, or 1,10-phenanthroline. Particulate 02-produc- tion accounted for 35% of the oxygen taken up during the respiratory burst by an equivalent number of intact neutrophils.