A Nickel-Alkyl Bond in an Inactivated State of the Enzyme Catalyzing Methane Formation

摘要

The cobalt-carbon bonds of methyl cobalamin and adenosyl cobalamin are the only transition-metal-alkyl bonds verified to date in the active site of enzymes.Methyl-nickel bonds have been postulated to be formed during two enzyme-catalyzed steps,for which,however,experimental evidence has not been provided.These reactions are the synthesis of acetyl-coenzyme A from methyl tetrahydrofolate,carbon monoxide,and coenzyme A when catalyzed by acetyl-coenzyme A synthase(decarbonylase),and methane formation from methyl-coenzyme M and coenzyme B when catalyzed by methyl-coenzyme M reductase(MCR).