The enzymatic mechanism of glucuronidation catalyzed by two purified rat liver steroid UDP-glucuronosyltransferases.
A kinetic analysis of two homogeneous rat liver steroid (3 alpha-hydroxysteroid and 17 beta-hydroxysteroid) UDP-glucuronosyltransferases was conducted using bisubstrate kinetic analysis, product inhibition studies, and dead-end competitive inhibition studies. Double reciprocal plots of initial velocity versus substrate concentration, using bisubstrate kinetic analysis, gave a sequential mechanism. Product inhibition studies were compatible with either a rapid equilibrium, random-order kinetic mechanism or an ordered Theorell-Chance mechanism. Results of dead-end competitive inhibition studies excluded an ordered Theorell-Chance mechanism. The cumulative results are consistent with a rapid equilibrium random-order sequential kinetic mechanism for the glucuronidation of testosterone by purified 17 beta-hydroxysteroid UDP-glucuronosyltransferase and of androsterone by purified 3 alpha-hydroxysteroid UDP-glucuronosyltransferase.[1]References
- The enzymatic mechanism of glucuronidation catalyzed by two purified rat liver steroid UDP-glucuronosyltransferases. Falany, C.N., Green, M.D., Tephly, T.R. J. Biol. Chem. (1987) [Pubmed]
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