Cell-wall-bound proteinase of Lactobacillus delbrueckii subsp. lactis ACA-DC 178: Characterization and specificity for beta-casein

Lactobacillus delbrueckii subsp. lactis ACA-DC 178, which was isolated from Greek Kasseri cheese, produces a cell-wall-bound proteinase. The proteinas e was removed from the cell envelope by washing the cells with a Ca2+-free buffer. The crude proteinase extract shows its highest activity at pH 6.0 a nd 40 degrees C. It is inhibited by phenylmethylsulfonyl fluoride, showing that the enzyme is a serine-type proteinase. Considering the substrate spec ificity, the enzyme is similar to the lactocaccal P-1-type proteinases, sin ce it hydrolyzes beta-casein mainly and alpha- and K-caseins to a much less er extent. The cell-wall-bound proteinase from L. delbrueckii subsp. lactis ACA-DC 178 liberates four main peptides from beta-casein, which have been identified.