Superoxide production by cytochrome b559. Mechanism of cytosol-independent activation.

摘要: Purified cytochrome b559 relipidated with either a mixture of phosphatidylcholine and phosphatidic acid or only exhibits high low superoxide (O2-) producing ability, respectively, in the absence cytosolic activators [Koshkin, V. Pick, E. (1993) FEBS Lett. 327, 57-62]. This system was used as model for study mechanism NADPH oxidase activation. It is shown that, depending on composition phospholipid environment, b599 binds FAD affinity, this being accompanied by changes flavin absorbance fluorescence. High affinity binding to combined associated an enhanced NADPH-driven O2- capacity. A kinetic production reflavinated under stoichiometric conditions revealed FAD/heme ratio 1:2. further high- low-activity b559, at varying substrate concentrations, determination steady-state difference spectra such preparations, reduced NADPH, indicated that activated facilitation electron transfer from rather than enhancement binding.