Browse by author
Lookup NU author(s): Hitesh Motwani, Emeritus Professor Bernard Golding
Full text for this publication is not currently held within this repository. Alternative links are provided below where available.
The reduced state of vitamin B-12, cob(I)alamin, acts as a supernucleophile that reacts ca. 10(5) times faster than standard nuclephiles, for example, thiols. Methods have been developed for trapping electrophilically reactive Compounds by exploiting this property of cob(I)alamin. 1,3-Butadiene (BD) has recently been classified as a group I human carcinogen by the International Agency for Research on Cancer (IARC). The carcinogenicity of BD is considered to be dependent on the activation or deactivation of the reactive metabolites of BD, that is, the epoxides (oxiranes) 1,2-epoxy-3-butene (EB), 1,13,4-diepoxybutane (DEB), and 1,2-epoxy-3,4-butanediol (EBdiol). Cytochrome P450 (P450) isozymes are involved in oxidation of BD to EB and further activation to DEB. EB and DEB are hydrolyzed by epoxide hydrolases (EH) to 3,4-dihydroxy-1-butene (BDdiol) and EBdiol, respectively. EBdiol can also he formed by oxidation of BDdiol. In the present study, cob(I)alamin was used for instant trapping of the BD epoxide metabolites generated in in vitro metabolism to Study enzyme kinetics. The Substrates EB, DEB. and BDdiol were incubated with rat S9 liver fraction. and apparent K-m and apparent V-max, were determined. The ratio of conversion of EB to DEB (by P450) to the rate of deactivation of DE13 by EH was 1.09. Formation of EBdiol from hydrolysis of DEB was ca. 10 times faster than that from oxidation of BDdiol. It was also found that the oxidation of EB to DEB was much faster than that of BDdiol to EBdiol. The Study offers comparative enzyme kinetic data of different BD metabolic Steps. which is useful for quantitative interspecies comparison. Furthermore, a new application of cob(I)alamin was demonstrated for the measurement of enzyme kinetics Of compounds that form electophilically reactive metabolites.
Author(s): Motwani HV, Fred C, Hagolund J, Golding BT, Tornqvist M
Publication type: Article
Publication status: Published
Journal: Chemical Research in Toxicology
Year: 2009
Volume: 22
Issue: 9
Pages: 1509-1516
ISSN (print): 0893-228X
ISSN (electronic): 1520-5010
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/tx900088w
DOI: 10.1021/tx900088w
Altmetrics provided by Altmetric
