Intrinsic dichlorophenolindophenol reductase activity associated with the superoxide-generating oxidoreductase of human granulocytes.
NADPH-dependent dichlorophenolindophenol ( DCIP) reductase activity cosediments with NADPH-dependent O(2-)-generating activity in subcellular particulate fractions of zymosan-stimulated human polymorphonuclear leukocytes (PMN's). Subcellular fractions derived from unstimulated PMN's were devoid of both activities, as were fractions from zymosan-stimulated PMN's of a patient known to have chronic granulomatous disease. NADPH-dependent DCIP reduction associated with the oxidoreductase-rich subcellular fractions was unaffected by addition of excess superoxide dismutase sufficient to abolish all traces of O2- production as measured by conversion of ferricytochrome c to its ferrous form. Moreover, DCIP inhibited NADPH-dependent production of O2- in subcellular fractions derived from normal donors. In contrast to the subcellular studies, whole cell suspensions were ineffective in reducing extracellular DCIP despite their capacity to generate O2-, albeit at a lesser rate, in the presence of this electron-accepting dye. These results demonstrate that DCIP reductase activity is associated with the oxidoreductase complex and suggest that it is located on the inner side of the PMN's plasma membrane. The stability of the oxidoreductase complex is markedly improved by storage in glycerol. Both overall O(2-)-generating activity and DCIP reductase activity exhibit a similar pH optimum of 7. 0. The Km of the oxidoreductase complex for DCIP is 33 micro M.[1]References
- Intrinsic dichlorophenolindophenol reductase activity associated with the superoxide-generating oxidoreductase of human granulocytes. Green, T.R., Schaefer, R.E. Biochemistry (1981) [Pubmed]
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