CELL-WALL ASSOCIATED PEPTIDE-HYDROLASE AND ESTERASE-ACTIVITIES IN SEVERAL CHEESE-RELATED BACTERIA

Cell-wall associated proteinases, peptidases and esterases of Lactobac illus helveticus, Pediococcus sp., Leuconostoc mesenteroides ssp. mese nteroides, Brevibacterium linens, Propionibacterium acidipropionici an d Bifidobacterium infantis were assayed. Proteolytic activity was meas ured using C14-labelled casein. Aminopeptidase, dipeptidase and estera se activities were measured using chromogenic substrates. All the chee se related bacteria tested exhibited cell-wall proteinase activities w ith highest being detected in Leuconostoc mesenteroides ssp. mesentero ides, Pediococcus sp. and Brevibacterium linens. Lactobacillus helveti cus and Brevibacterium linens exhibited greater cell-wall esterase and aminopeptidase activities, but little of the total activities of thes e enzymes were associated with the cell envelope. Greater properties o f total cellular dipeptidase activities were associated with the cell envelope, with Lactobacillus helveticus and Brevibacterium linens exhi biting highest specific activities. The optimum pH of the crude cell-w all proteinase of different strains ranged from pH 5.5 to 8.0 while th e optimum temperature ranged from 20 to 40-degrees-C. The impact of pr oteinase inhibitors tested differed between species.