A menadione-stimulated pyridine nucleotide oxidase from resting bovine neutrophil membranes. Purification, properties, and immunochemical cross-reactivity with the human neutrophil NADPH oxidase

Abstract

A menadione-stimulated, superoxide-generating enzyme was purified 127-fold from resting bovine polymorphonuclear leukocyte (neutrophil) membranes with a yield of 34%. The enzyme was extracted with Triton X-100 and purified by chromatography on DEAE-Sepharose CL-6B, NAD-agarose, and Sephacryl S-200. The purified enzyme contained FAD and had an apparent molecular mass of 93 kDa by sodium dodecyl sulfate gel electrophoresis. In a nondenaturing gel electrophoresis system, the enzyme was multimeric (Mr greater than 400,000). The oxidase showed 3-4-fold higher activity (Vm) with NADH compared with NADPH, but the Km for both pyridine nucleotides was similar (39 and 47 microM, respectively). The enzyme transferred electrons to cytochrome c, dichlorophenolindophenol, and nitro blue tetrazolium. Cytochrome c reduction was stimulated 4-fold by menadione and was inhibited 70% by superoxide dismutase. Cytochrome c reduction was not inhibited by several mitochondrial respiratory chain inhibitors (azide, cyanide, and rotenone) but was sensitive to thiol-reactive agents (p-chloromercuribenzoate and monoiodo acetate). The catalytic properties of this enzyme distinguish it from the NADPH-dependent superoxide-generating respiratory burst oxidase (NADPH-oxidase) of human neutrophils. Nevertheless, antibodies to this enzyme inhibited not only the purified menadione-stimulated oxidase, but also the respiratory burst oxidase in membranes isolated from activated human neutrophils, indicating similar antigenic determinants are shared by these enzymes. Western blots of human neutrophil membranes visualized a plasma membrane protein of molecular mass 67 kDa, corresponding in size to a protein previously reported in preparations of the human respiratory burst oxidase.