Kinetics of activation of the respiratory burst oxidase in a fully soluble system from human neutrophils.

In a fully soluble system from resting human neutrophils, activation of the respiratory burst oxidase under defined conditions was found to follow first-order kinetics. The manner in which this first-order activation process varied with the concentrations of the individual components in the activating system suggested the following. 1) The respiratory burst oxidase occurs in two forms that can be distinguished by their Km values for NADPH. The low-affinity form contains one component (M) from the membrane and two components (S and C alpha) from the cytosol, while the high-affinity form contains an extra cytosolic component (C beta). 2) The active forms of the oxidase are generated in the following reactions: (formula; see text) where S is a stabilizing component and where M.S is an activated form of M.S that is capable of binding C alpha and C beta to produce the active oxidase species M.S.C alpha (the low-affinity form) and M.S.C alpha C beta (the high-affinity form). 3) SDS activates the oxidase by mediating the conversion of M.S to M.S.