Human liver L-leucine aminopeptidase: evidence for two forms compared to pig liver enzyme

Two forms of L-leucine aminopeptidase (E.C. 3.4.11.1) having a specific activity toward L-leucine amide and L-leucylpeptides substrates but not toward chromogenic substrates: L-leucyl paranitroanilide or L-leucyl beta naphthylamide have been evidenced from human liver. Human liver enzymes have been distinguished from pig liver enzyme by DEAE Sephacel chromatography and analytical electrophoresis on cellulose acetate strips. We compared enzymic properties of L-leucine aminopeptidases from human liver with pig liver enzyme: they were activated by Mg2+ and Mn2+ and inhibited by Zn2+ and Co2+, EDTA and citric acid. The optimum pH's were 10. Both human liver L-leucine aminopeptidases were less sensitive to heat elevation than pig liver enzyme.