Characterization of Cell-Envelope Proteinases from Two Strains Isolated from Parmigiano Reggiano Cheese.

In the present work, two cell-envelope proteinases (CEPs) from strains PRA205 and 2006 were characterized at both the biochemical and genetic levels. The genomes of both strains included two putative CEPs genes and , but only was transcribed. The extracted PrtR1 proteinases were serine proteinases with optimal activity at 40 °C and pH 7.5, and were activated by Ca ions. Interestingly, PrtR1 from PRA205 exhibited high residual activity at pH 4 and at 5 °C, suggesting its possible exploitation for fermented food production. The caseinolytic activity against αS1- and β-casein indicated that both PrtR1s belonged to the PI/PIII type. These PrtR1s cleaved β-casein peptide bonds preferentially when amino acid M or N was present at the P1 subsite and amino acids A and D were at the P1' subsite. Several bioactive peptides were found to be released from PrtR1 after αs1- and β-casein hydrolysis.