Adenosylcobalamin (coenzyme B-12)-dependent glutamate mutase catalyzes a mo
st unusual carbon skeleton rearrangement involving the isomerization of L-g
lutamate to L-threomethylaspartate, a reaction that is without precedent in
organic chemistry. This reaction proceeds through a mechanism involving fr
ee radical intermediates that are initiated by homolysis of the cobalt-carb
on bond of the coenzyme. The enzyme serves as a paradigm for adenosylcobala
min-dependent catalysis and, more generally, provides insights into how enz
ymes generate and control reactive free radical species, This review descri
bes how recent studies on the mechanism and structure of glutamate mutase h
ave contributed to our understanding of adenosylcobalamin-mediated catalysi
s. (C) 2000 Academic Press.