Abstract
A new continuous monitoring method for the determination of leucine aminopeptidase (LAP) was presented. This method is based on the principle which consists of the measurement of ammonia liberated from the substrate leucineamide by the action of LAP with glutamate dehydrogenase as a coupling enzyme. Kinetical properties of glutamate dehydrogenase from Proteus inconstans used for the coupling system were studied and the optimum condition for the measuring of LAP was settled on the basis of the theory described by Horio et al.9
L-Leucine-β-naphthylamide and L-leucine-p-nitroanilide have been used as substrate for the determination of LAP in clinical laboratories. The activities of LAP which used these coventional chromogenic substrates (Arylamidase, A. A) and that of LAP presented in this study were compared in various diseases. Good correlation was obtained from both LAP and A. A activities in almost all cases of normal and hepatobiliary disorders, however, remarkable discrepancy was observed in both activities in the cases of hepatitis, malignant lymphoma and leukemias. It was suggested that the method presented in this study would be useful for the detection of these lymphomatosis and leukemic diseases.
