Purification of X-prolyl dipeptidyl aminopeptidase from Lactobacillus casei subspecies.

Prolyl dipeptidylaminopeptidases from two subspecies of Lactobacillus casei were purified and biochemically characterized. L. casei ssp. casei UL21 (a debittering strain) and L. casei ssp. rhamnosus UL26 (a non-debittering strain) were the source bacteria for this study. Purification of the enzymes from both the sources was effected by a gel filtration step through Sephacryl S-300 followed by ion-exchange chromatography through DEAE Sephacel. This rendered an electrophoretically homogeneous enzyme preparation. The purified enzymes from both the sources showed similar temperature optimum (45 degrees C) and pH optimum (7.0). Their activity profiles on various substrates and the nature of inhibition by different inhibitors were also found to be similar, indicating that this enzyme is perhaps not significantly involved in the debittering process during the maturation of cheese.