Isolation of the respiratory burst oxidase: The role of a flavoprotein component

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Abstract
The article reviews the enzymatic and electron transfer properties of a low-potential FAD-dependent flavoprotein that is a component of the NADPH-dependent O −2 · -generating respiratory burst oxidase of phagocytes. Current methods available for isolation of the respiratory burst oxidase and the flavo-protein component of the complex are also reviewed. These studies and data obtained from affinity-labeling of respiratory burst oxidase components, suggest that the flavoprotein has a molecular weight of 65–67 kD. The prevailing evidence suggests that the flavoprotein functions as a dehydrogenase/electron transferase and can directly catalyse NADPH-dependent O −2 · formation when isolated. However, in neutrophil plasma membranes, the prevailing evidence suggests that the flavoprotein functions primarily to transfer electrons from NADPH to cytochromeb −245 and that this latter redox component is the catalytic side of O −2 · formation. A working model for the arrangement of the flavorprotein and cytochromeb −245 components of the respiratory burst oxidase in neutrophil membranes is proposed.