Stereochemistry of an alpha, beta-elimination reaction by D-glucosaminate dehydratase.

R Iwamoto, Y Imanaga, S Sawada, K Soda

Index: FEBS Lett. 156(1) , 33-6, (1983)

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Abstract

The proton NMR analysis of D-glucosaminate dehydratase reaction in D2O revealed the incorporation of a deuterium atom at C-3 carbon of the product, 2-keto-3-deoxy-D-gluconate. Based on the chemical shift of C-3 proton of the product and the coupling constant characteristic for the C-3 and C-4 axial-axial coupling in the 2C5 pyranose conformation, the deuterium is in the pro-S position. Thus, the dehydration of D-glucosaminate by the enzyme proceeds in a retention mode at C-3 carbon. Kinetic parameters show that the rate-determining step is the abstraction of alpha-proton from the substrate.