A spectrophotometric method for the determination of aminopeptidase activity with leucine dehydrogenase.

L-Leucine dehydrogenase purified from Bacillus megaterium and Bacillus sphearicus was used for the determination of serum aminopeptidase activity with L-leucinamide as a substrate. L-Leucine produced by aminopeptidase was determined by measurement of the increase in absorbance at 340 nm caused by the formation of NADH. This method is useful for the kinetic studies of the aminopeptidase and the enzyme assay of a large number of samples. The serum aminopeptidase can be characterized to give some valuable information in clinical diagnosis by comparison of the results obtained by the present method with those by the conventional method with L-leucyl-p-nitroanilide as a substrate.