Serumα-Hydroxybutyrate Dehydrogenase Activity: An Improved Method

Abstract

Utilizing purified commercial lactate dehydrogenase isoenzymes, human heart and liver supernatants, and sera from patients with myocardial infarction and hepatobiliary disease, a study of the optimal conditions for determination of α-hydroxybutyrate dehydrogenase activity has been made. The pH optima and K_m for each preparation were temperature-dependent. Lower pH and higher α-ketobutyrate concentrations were necessary at 37 C. than at 25 C. Despite the fact that LD1 and heart supernatant had lower values for K_m and higher values for the Energy of Activation than LD5 and liver supernatant, sera from patients with myocardial infarction and hepatobiliary disease showed little difference in these respects. An improved method for measuring α-hydroxybutyrate dehydrogenase activity of human serum at 37 C. is described, in comparison with which four commercial kits gave much lower values. The upper normal limit for the proposed method is 417 I.U. per 1.