title: NADPH-cytochrome c reductase from human neutrophil membranes: purification, characterization and localization.
abstract: Neutrophil-membrane-associated NADPH-cytochrome c reductase and cytochrome b558 were separately eluted and highly purified by a combination of ion-exchange Sepharose, N-amino-octylagarose, 2',5'-ADP-Sepharose and heparin-Sepharose column chromatographies. The purified cytochrome c reductase with an apparent molecular mass of 68 kDa contained FMN and FAD (FMN/FAD approx. 1). Cytochrome b558 prepared in the presence of phospholipids and FAD showed marked O2-.-producing activity (Vmax., 8.53 mumol of O2-./min per mg of cytochrome; Km for NADPH 58.8 microM) in a cell-free assay system consisting of cytosol, arachidonate and GTP[S]. However, when it was obtained without FAD added to the purification process, it had negligible FAD and little or no O2-.-forming activity in the reconstituted system. The NADPH oxidase activity was not markedly stimulated on incubation of the purified reductase with either flavinated or flavin-depleted cytochrome b558 in the cell-free system, suggesting that the reductase is not likely to be involved in neutrophil O2-. generation. The purified reductase cross-reacted with polyclonal antibodies against both hepatic NADPH-cytochrome P-450 reductase and a synthetic peptide, ILVGPGTGIAPFRSF, which indicates residues 529-543 located in the glycine-rich NADPH-binding domain of the P-450 reductase, but cytochrome b558 did not produce any immunoreactive bands to these antibodies. These antibodies also produced a positive reaction with a 76 kDa protein from dimethyl sulphoxide-induced HL-60-cell microsomes. After solubilization of the microsomal membranes, the 76 kDa protein was readily converted into a partially proteolysed form (68 kDa) even in the presence of antiproteases. In addition, the microsomal fraction shows a CO difference spectrum with a peak at about 454 nm and a trough at 476 nm in the presence of dithionite, indicating the presence of a cytochrome P-450-like haemoprotein.
authors.affiliation: Department of Biochemistry, Aichi Medical University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nisimoto
authors.forename: H
authors.initials: H
authors.lastname: Otsuka-Murakami
authors.forename: S
authors.initials: S
authors.lastname: Iwata
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D002248:Carbon Monoxide; D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003573:Cytochrome b Group / Q000302:isolation & purification / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008861:Microsomes / Q000201:enzymology; D008969:Molecular Sequence Data; D019255:NADPH Oxidases; D009251:NADPH-Ferrihemoprotein Reductase / Q000302:isolation & purification* / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology*
chemical_list: D003573:Cytochrome b Group; D002248:Carbon Monoxide; C036888:cytochrome b558; D009251:NADPH-Ferrihemoprotein Reductase; D019255:NADPH Oxidases