A zinc-dependent proteinase from the cell wall of Lactobacillus delbrueckii subsp. bulgaricus.

A zinc-dependent proteinase was extracted from the cell wall of Lactobacillus delbrueckii subsp. bulgaricus and partially purified despite a marked unstability. The caseinolytic activity was associated with a polypeptide chain of 65 kDa that belonged to the M1 family of zinc-dependent proteases. This zinc-dependent proteinase could degrade intact caseins, with a significant preference for beta-casein. The pH-profile of its activity indicated that its relative contribution to the caseinolytic activity increased at acidic pH, suggesting that this zinc proteinase could be involved in the late stages of milk fermentation.