Evidence that Ferredoxin Interfaces with an Internal Redox Shuttle in Acetyl-CoA Synthase During Reductive Activation and Catalysis

摘要: Acetyl-CoA synthase (ACS), a subunit of the bifunctional CO dehydrogenase/acetyl-CoA (CODH/ACS) complex Moorella thermoacetica requires reductive activation in order to catalyze acetyl-CoA synthesis and related partial reactions, including CO/[1-14C]-acetyl-CoA exchange reaction. We show that M. ferredoxin(II) (Fd-II), which harbors two [4Fe-4S] clusters is an electron acceptor for CODH, serves as redox activator ACS. The level depends on oxidation states both ACS Fd-II, strongly suggests Fd-II acts reducing agent. By use controlled potential enzymology, midpoint reduction catalytic one-electron redox-active species CO/acetyl-CoA reaction −511 mV, similar was earlier measured other reactions involving Incubation with leads formation NiFeC species, also supports role Fd-II...