Existence of Three Forms of H₂M₂ Isoenzyme of Lactate Dehydrogenase

Abstract

Lactate dehydrogenase (LDH) was purified from rat and bovine tissues by affinity chromatography on immobilized colchicine and used for the separation of isoenzymes by high-performance anion-exchange liquid chromatography (HPLC). This analysis showed the splitting of rat H₂M₂ into three peaks and of bovine H₂M₂ into two peaks. The heat stability, inactivation rate of urea and electrophoretic mobility of isoenzymes were examined and these analyses indicated differences in physicochemical properities for the respective peaks of rat and bovine H₂M₂. In hybridization experiments, the splitting of H₂M₂ into three peaks was achieved only with the combination of rat H₄ and rat M₄, while the other combinations of bovine H₄ and bovine M₄, of rat H₄ and M₄ and of bovine H₄ and rat M₄ resulted in two H₂M₂ peaks.These results demonstrate that H₂M₂ of LDH in normal rat and bovine tissues is always split into two or three peaks by HPLC and that these H₂M₂ peaks have different physicochemical propertites, suggesting the existence of three possible geometrical isomers of H₂M₂.