Original features of cell-envelope proteinases of Lactobacillus helveticus. A review.

Lactobacillus helveticus is a lactic acid bacterium very used in fermented milks and cheese. The rapid growth of L. helveticus in milk is supported by an efficient cell envelope proteinase (CEP) activity, due to subtilisin-like serine proteases. These enzymes play also crucial roles in texture and flavor formation in dairy products as well as in generating in situ bioactive peptides. In L. helveticus, several genes encoding putative CEPs were detected and characterized by a large intraspecific diversity; little is known about regulation of expression of CEP-encoding genes. Anchored at the bacterial surface, CEPs are large-sized enzymes (> 150 kDa) hydrolyzing β- and α(s1)-casein as well. Substrate cleavages occur after almost all types of amino acids residues, but mass spectrometry analysis revealed L. helveticus strains with specific profiles of substrate hydrolysis, which could explain identification of strains associated with interesting technological properties. In this review, the most recent data regarding CEP-encoding genes, CEP activities toward caseins and L. helveticus strain diversity are discussed.