Proton transfer in methylmalonyl-CoA epimerase from Propionibacterium shermanii. The reaction of (2R)-methylmalonyl-CoA in tritiated water
- 1 September 1983
- journal article
- research article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 213 (3), 643-650
- https://doi.org/10.1042/bj2130643
Abstract
The reaction catalysed by methylmalonyl-CoA epimerase from Propionibacterium shermanii was studied in tritiated water, in the direction with (2R)-methylmalonyl-CoA as substrate, under ‘irreversible’ conditions. After partial reaction, even when most of the substrate had been converted into product (isolated as propionyl-CoA) essentially no solvent tritium appeared in residual (2R)-methylmalonyl-CoA. The product, however, did contain tritium, and the specific radioactivity of the (2S)-epimer was deduced to be 0.33 times that of the solvent. These results provide further support for the mechanism proposed for the epimerase-catalysed reaction in the accompanying paper [Leadlay & Fuller (1983) Biochem. J. 213, 635-642], in which two enzyme bases act respectively as proton donor and acceptor. The observed low discrimination against solvent tritium entering the product can be accounted for by a mechanism in which the release of product is slow, and the re-protonation step on the enzyme is reversible, without leading to isotopic exchange with the solvent.This publication has 16 references indexed in Scilit:
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