γδ-Dioxovalerate as a substrate for the glyoxalase enzyme system

Crude gammadelta-dioxovalerate was synthesized from laevulinate by two different methods and was purified by Sephadex chromatography. Some analytical reactions of the compound are described. 2. gammadelta-Dioxovalerate is a substrate for glyoxalase I and the GSH derivative formed by this enzyme is hydrolysed by glyoxalase II to form d-alpha-hydroxyglutarate. The K(m) of glyoxalase I for gammadelta-dioxovalerate is 1.0x10(-3)m at pH5.8.3. The u.v.-absorption spectrum of thiol ester, synthesized enzymically from gammadelta-dioxovalerate and GSH by glyoxalase I, is almost identical with that for S-lactoylglutathione. Some optical properties of this thiol ester were measured. 4. Attempts to show reversibility of the glyoxalase system reactions with d-alpha-hydroxyglutarate as substrate were unsuccessful. 5. The possible metabolic role of the gammadelta-dioxovalerate reaction is discussed. It is suggested that one of the metabolic functions of the glyoxalase system may be to provide a mechanism for the entry of this compound into the tricarboxylic acid cycle.