Proteolytic activity of mycoplasmas and ureaplasmas isolated freshly from human saliva.

Mycoplasma and Ureaplasma strains freshly isolated from human saliva were examined for proteolytic activity. All the strains tested (101 strains of Mycoplasma salivarium, 97 strains of Mycoplasma orale, and 3 strains each of Mycoplasma hominis and Ureaplasma urealyticum) decomposed horse serum proteins, bovine albumin, and casein. Ten of the M. salivarium and 8 of the M. orale strains were tested for aminopeptidase activity as well, using L-leucine-p-nitroanilide as a substrate, and were shown to possess the activity. Thus proteolytic activity was suggested to be one of the biological characteristics of these two species. The level of both caseinolytic and aminopeptidase activity was significantly higher in M. salivarium than M. orale strains.