[Detection and properties of L-threonine-L-serine dehydratase in human liver]

It has been shown that in liver extract of men deceased by different causes, L-threonine and L-serine dehydratase activities probably, belonging to only one enzyme--L-threonine-L-serine dehydratase--are found. Both activities and their ratios depend on K+ concentration both in the buffer used for enzyme extraction and in the reaction medium. Before extraction of active and stable forms of enzyme the liver is to homogenized in a buffer containing 0.15 M KCl. Both enzymatic activities have a pH-optimum at pH 9.6--10.0. It was shown that D-isomers of threonine and serine are not dehydratated and do not inhibit dehydratation of L-isomers. Studies of dependence of L-threonine and L-serine dehydratase reaction rates on temperature showed that at any temperature ranges the energy activation values are higher for the L-threonine dehydratase reaction than for the L-serine dehydratase reaction and that the ratio reaction rates for both reactions depends on temperature.