PURIFICATION AND CHARACTERIZATION OF A TRIPEPTIDASE FROM LACTOBACILLUS-SAKE

A tripeptidase was purified to homogeneity from the cell extract of La ctobacillus sake by ammonium sulfate precipitation, hydrophobic intera ction chromatography, gel filtration chromatography, and two steps of anion exchange chromatography. After SDS-PAGE a single band of protein was detected of approximately 55 kDa. A similar molecular mass was es timated by gel filtration. The tripeptidase activity was optimal at pH 7.0 and at 40 degrees C. The enzyme was strongly inhibited by metal c helators, reducing agents, and bestatin while thiol group reagents, se rine proteinase inhibitors, and aspartic proteinase inhibitors had no effect on the activity. The enzyme was activated by Mn2+ and almost to tally inhibited by Zn2+ and to a lesser extent by Sn2+. The enzyme onl y exhibited activity against tripeptides, and those hydrolyzed at high er rates were Ala-Ala-Ala, Ser-Ser-Ser, and Leu-Gly-Gly.