Les peptide-hydrolases des lactobacilles du groupe Thermobactetium. I. Mise en évidence de ces activités chez Lactobacillus helveticus, L. acidophilus, L. lactis et L. bulgaricus

Abstract

The intracellular peptide hydrolase activities of Lactobacillus helveticus, L. acidophilus, L. lactis, and L. bulgaricus were determined using various aminopeptidase, dipeptidase, and carboxypeptidase substrates in addition to casein and whey protein fractions. The different activities were then separated using disc gel electrophoresis. Each bacterium had aminopeptidase activity towards various amino acid β-naphthylamides and dipeptides. The four species also showed bands of true dipeptidase activities on a large number of dipeptides. Intracellular enzymes from thermophilic lactobacilli also hydrolysed the whey proteins (α-lactalbumin and β-lactoglobulin). From the results of electrophoresis on β-casein and α_s1-casein it was shown that β-casein was totally hydrolysed by L. lactis while it was only partially hydrolysed by the intracellular enzymes of L. acidophilus and L. bulgaricus. On the other hand, α_s1-casein was only partially hydrolysed by L. helveticus, L. lactis, and L. bulgaricus.