A chloride activated alanine aminopeptidase from a melanoma cell line

Alanine aminopeptidase was partially purified from cultured human melanoma cells (Bowes) by gel filtration on Sephadex G-200 and DEAE Sepharose column chromatography. The molecular weight of the enzyme was about 52,000 as determined by gel filtration on Sephadex G-100. The enzyme hydrolyzed L-alanine beta-naphthylamide (NA), but not or slightly L-methionine-NA, L-leucine-NA, and L-arginine-NA. The Km value for L-alanine-NA was 0.17 mmol/l, pH optimum was 7.4. The enzyme was stable at 50 degrees C for 20 min, but lost about 50% of its activity at 60 degrees C within 20 min. It was markedly stimulated by chloride ions, and was inhibited by sulfhydryl blocking agents and EDTA. The activity was restored by the addition of Co2+ or Zn2+ after EDTA treatment. The enzyme is a metallo- and thiol-dependent and chloride-activated, low-molecular weight aminopeptidase.