Aminopeptidase and caseinolytic activities of Mycoplasma salivarium.

Aminopeptidase activity was demonstrated in Mycoplasma salivarium (ATCC 23064) cells disrupted by sonic vibrations and lyophilized (crude enzymes), and weak endopeptidase or carboxypeptidase activity was also suggested. The crude enzymes were suspended in 0.1 M borate buffer, pH 8.0, containing 0.5% (w/v) sodium deoxycholate, and then the suspensions were centrifuged at 100,000 g for 2 h. Thus separated, the supernatants were applied to a column of Sephacryl S-300. As a result, aminopeptidase activity was separated from caseinolytic activity, which had already been demonstrated in this organism. The aminopeptidase activity was inhibited by o-phenanthroline and stimulated by Mn2+, and the enzyme exhibited a strong affinity for leucine and arginine. On the other hand, the caseinolytic activity was inhibited considerably by o-phenanthroline and Ni2+ and slightly by diisopropyl fluorophosphate and Co2+. The caseinolytic activity was therefore believed to be due mainly to metalloproteinases and partly to serine proteinases.