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Published April 27, 1979 | public
Journal Article

Stereospecificity and mechanism of adenosylcobalamin-dependent diol dehydratase. Catalysis and inactivation with meso- and dl-2,3-butanediols as substrates

Abstract

A comparative study of the reaction of meso-, d-, and dl-2,3-butanediols with adenosylcobalamin-dependent dioldehydratase was carried out. While the meso isomer is both a substrate and inactivator of holoenzyme, the d and dl compounds act as purely competitive inhibitors, neither undergoing catalysis nor inactivating holoenzyme. Furthermore, d- and dl-2,3-butanediols protect holoenzyme from oxygen inactivation and enzyme-bound cofactor from photolysis, and do not induce detectable cleavage of the carbon-cobalt bond of cofactor. These results show that the stereospecificity of the inactivation reaction is the same as that of catalysis, suggest that hydrogen abstraction from C-1 of substrate may be concerted with cleavage of the carbon-cobalt bond of adenosylcobalamin, and further suggest that formation of a carbon-cobalt bond between coenzyme and substrate is not obligatory for catalysis.

Additional Information

© 1979 by Academic Press, Inc. Received 26 February 1979, Available online 6 April 2005. The authors thank Drs. M. A. Raftery and M. Schimerlik for use of the Cary 118 spectrophotometer. This research was supported by National Institutes of Health Grant No. GM-10218.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023