The pH dependence of NADPH oxidase in human eosinophils.

摘要: NADPH oxidase generates reactive oxygen species that are essential to innate immunity against microbes. Like most enzymes, it is sensitive pH, although the relative importance of pH(o) and pH(i) has not been clearly distinguished. We have taken advantage electrogenic nature determine its pH dependence in patch-clamped individual human eosinophils using electron current indicate enzyme activity. Electron stimulated by PMA (phorbol myristate acetate) was recorded both perforated-patch configuration, an NH4+ gradient control pH(i), excised, inside-out patches membrane. No detected cells or excised from a patient with chronic granulomatous disease. When varied symmetrically (pH(o) = pH(i)) oxidase-generated maximal at 7.5, decreasing drastically higher lower values. Varying independently revealed this entirely due effects insensitive pH(o). Surprisingly, membrane only weakly indicating turnover rate per se strongly dependent. The likely interpretation assembly deactivation complex one more pH-sensitive steps, pH-dependent changes intact mainly reflect different numbers active complexes pH.