A new method for peptidase activity measurement in serum and tissues, using L-Leu-L-Leu as substrate

Peptidase-free L-amino-acid oxidase was purified from venom of Agkistrodon caliginosus and was used for the determination of serum peptidase (EC 3.4.1.-) activity with L-Leu-L-Leu as substrate. The peptidase activity in human serum rose remarkably in liver diseases, and had a significant correlation with serum transaminase activity. The peptidase activity in serum of rats treated with CCl4 was higher than that of normal rats. After Cellogel electrophoresis the zymogram of peptidase from human liver using di- or tripeptide as substrate appeared with three active bands; however, peptidase in serum of a patient with acute hepatitis showed only one active band.