CaltechAUTHORS
  A Caltech Library Service

Mechanism of action of adenosylcobalamin: glycerol and other substrate analogs as substrates and inactivators for propanediol dehydratase - kinetics, stereospecificity, and mechanism

Bachovchin, William W. and Eagar, Robert G., Jr. and Moore, Kevin W. and Richards, John H. (1977) Mechanism of action of adenosylcobalamin: glycerol and other substrate analogs as substrates and inactivators for propanediol dehydratase - kinetics, stereospecificity, and mechanism. Biochemistry, 16 (6). pp. 1082-1092. ISSN 0006-2960. http://resolver.caltech.edu/CaltechAUTHORS:20150505-101355162

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20150505-101355162

Abstract

A number of vicinal diols were found to react with propanediol dehydratase, typically resulting in the conversion of enzyme-bound adenosylcobalamin to cob(Il)alamin and formation of aldehyde or ketone derived from substrate. Moreover, all are capable of effecting the irreversible inactivation of the enzyme. The kinetics and mechanism of product formation and inactivation were investigated. Glycerol, found to be a very good substrate for diol dehydratase as well as a potent inactivator, atypically, did not induce cob(II)alamin formation to any detectable extent. With glycerol, the inactivation process was accompanied by conversion of enzymebound adenosylcobalamin to an alkyl or thiol cobalamin, probably by substitution of an amino acid side chain near the active site for the 5'-deoxy-5'-adenosyl ligand on the cobala-min. The inactivation reaction with glycerol as the inactivator exhibits a deuterium isotope effect of 14, strongly implicating hydrogen transfer as an important step in the mechanism of inactivation. The isotope effect on the rate of product formation was found to be 8.0. Experiments with isotopically substituted glycerols indicate that diol dehydrase distinguishes between "R" and "S" binding conformations, the enzyme-(R)-glycerol complex being predominately responsible for the productforming reaction, while the enzyme-(S)-glycerol complex results primarily in the inactivation reaction. Mechanistic implications are discussed. A method for removing enzymebound hydroxycobalamin that is nondestructive to the enzyme and a technique for measuring the binding constants of (R) and (S)-1,2-propanediols are presented.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/bi00625a009DOIArticle
http://pubs.acs.org/doi/abs/10.1021/bi00625a009PublisherArticle
Additional Information:© 1977 American Chemical Society. Received August 14, 1976. This research was supported by National Institute of Health Grant GM-10218. The authors gratefully acknowledge Mamoru Nakatsui for his help in the synthesis of several of the substrates.
Funders:
Funding AgencyGrant Number
NIHGM-10218
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Church Laboratory of Chemical Biology5363
Record Number:CaltechAUTHORS:20150505-101355162
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150505-101355162
Official Citation:Mechanism of action of adenosylcobalamin: glycerol and other substrate analogs as substrates and inactivators for propanediol dehydratase - kinetics, stereospecificity, and mechanism William W. Bachovchin, Robert G. Eagar Jr., Kevin W. Moore, and John H. Richards Biochemistry 1977 16 (6), 1082-1092 DOI: 10.1021/bi00625a009
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57225
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:05 May 2015 19:33
Last Modified:05 May 2015 19:33

Repository Staff Only: item control page