Stereochemistry of the reaction of sheep liver threonine dehydratase. A nuclear magnetic resonance and optical rotatory dispersion study of its reaction pathway and products

Publisher Website
Google Scholar
Abstract
Products, substrates and inhibitors of the threonine dehydratase from sheep liver (EC 4.2.1.16) were investigated by proton NMR and optical rotation. The .alpha.-ketobutyrates produced from L-threonine and L-allothreonine in 2H2O incorporated a single 2H into the .beta. position. The dehydratase forms R-.alpha.-ketobutyrate-.beta.-d from L-threonine and L-allothreonine. The .alpha. protons of the substrates, threonine and allothreonine, do not exchange in the presence of the dehydratase. In the presence of dehydratase, the competitive inhibitors L-cysteine and L-alanine undergo .alpha.-proton exchange. Highly purified dehydratase was used to determine kinetic parameters for the substrates L-threonine, L-allothreonine, L-serine and L-chloroalanine. L-Chloroalanine is a substrate, and inhibits the dehydratase in a manner kinetically identical with that of L-serine.