Skip Navigation


Journal of Biochemistry Advance Access originally published online on June 27, 2008
Journal of Biochemistry 2008 144(4):437-446; doi:10.1093/jb/mvn086
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
144/4/437    most recent
mvn086v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Request Permissions
Google Scholar
Right arrow Articles by Toraya, T.
Right arrow Articles by Mori, K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Toraya, T.
Right arrow Articles by Mori, K.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 2008 The Japanese Biochemical Society.

Mechanism-based Inactivation of Coenzyme B12-dependent Diol Dehydratase by 3-Unsaturated 1,2-Diols and Thioglycerol

Tetsuo Toraya*, Naohisa Tamura, Takeshi Watanabe, Mamoru Yamanishi, Naoki Hieda and Koichi Mori

Department of Bioscience and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Okayama 700-8530, Japan

*To whom correspondence should be addressed. Tel: +81-86-251-8194, Fax: +81-86-251-8264, E-mail: toraya{at}cc.okayama-u.ac.jp

Received June 5, 2008; Accepted June 22, 2008


  Abstract

The reactions of diol dehydratase with 3-unsaturated 1,2-diols and thioglycerol were investigated. Holodiol dehydratase underwent rapid and irreversible inactivation by either 3-butene-1,2-diol, 3-butyne-1,2-diol or thioglycerol without catalytic turnovers. In the inactivation, the Co–C bond of adenosylcobalamin underwent irreversible cleavage forming unidentified radicals and cob(II)alamin that resisted oxidation even in the presence of oxygen. Two moles of 5'-deoxyadenosine per mol of enzyme was formed as an inactivation product from the coenzyme adenosyl group. Inactivated holoenzymes underwent reactivation by diol dehydratase-reactivating factor in the presence of ATP, Mg2+ and adenosylcobalamin. It was thus concluded that these substrate analogues served as mechanism-based inactivators or pseudosubstrates, and that the coenzyme was damaged in the inactivation, whereas apoenzyme was not damaged. In the inactivation by 3-unsaturated 1,2-diols, product radicals stabilized by neighbouring unsaturated bonds might be unable to back-abstract the hydrogen atom from 5'-deoxyadenosine and then converted to unidentified products. In the inactivation by thioglycerol, a product radical may be lost by the elimination of sulphydryl group producing acrolein and unidentified sulphur compound(s). H2S or sulphide ion was not formed. The loss or stabilization of product radicals would result in the inactivation of holoenzyme, because the regeneration of the coenzyme becomes impossible.

Key Words: adenosylcobalamin, coenzyme B12, diol dehydratase, mechanism-based inactivation, radical enzyme

Abbreviations: AdoCbl, adenosylcobalamin or coenzyme B12; aqCbl, aquacobalamin; DDR, diol dehydratase-reactivating factor; EPR, electron paramagnetic resonance; MBTH, 3-methyl-2-benzothiazolinone hydrazone; THF, tetrahydrofuran


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.