Photolysis and Recombination of Adenosylcobalamin Bound to Glutamate Mutase

J. Am. Chem. Soc., 126 (6), 1598 -1599, 2004. 10.1021/ja0396910 S0002-7863(03)09691-4
Web Release Date: January 23, 2004

Photolysis and Recombination of Adenosylcobalamin Bound to Glutamate Mutase

Roseanne J. Sension,* Allwyn G. Cole, Ahmasi D. Harris, Christel C. Fox, Neal W. Woodbury, Su Lin, and E. Neil G. Marsh*

Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry and Biochemistry and the Arizona Biodesign Institute, Arizona State University, Tempe, Arizona 85287-1604

rsension@umich.edu; nmarsh@umich.edu

Received November 19, 2003

Abstract:

Ultrafast spectroscopic measurements are used to determine the kinetics of homolysis and recombination for adenosylcobalamin bound in the active site of glutamate mutase. These are the first such measurements on an adenosylcobalamin-dependent enzyme. A short-lived intermediate is formed prior to formation of the cob(II)alamin radical. This intermediate was not observed upon photolysis of adenosylcobalamin in free solution. The intrinsic rate constant for geminate recombination for adenosylcobalamin bound to glutamate mutase is 1.08 ± 0.10 ns^-1, only 16% smaller than the rate constant measured in free solution, 1.39 ± 0.06 ns^-1, suggesting the protein does not greatly perturb the stability of the cobalt-carbon bond upon binding the coenzyme.

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