Proteolytic enzymes of lactic acid bacteria

The proteolytic system of lactic acid bacteria is essential for their growth in milk and contributes significantly to flavour development in fermented milk products where these microorganisms are used as starter cultures. The proteolytic system is composed of proteinases which initially cleave the milk protein to peptides, peptidases which cleave the peptides thus formed into smaller peptides and amino acids and transport systems which are involved in the cellular uptake of small peptides and amino acids. An overview of the literature on the research to date performed on the proteolytic enzymes of lactic acid bacteria is presented. The review highlights the different types of lactococcal and non-lactococcal proteinases as well as the approach to molecular cloning of the lactococcal proteinase genes and the molecular control of the regulation of proteinase production. A wide spectrum of peptidases have been identified in lactic acid bacteria. The research on the characterisation, substrate specificity and localisation of endopeptidases, aminopeptidases, dipeptidases, tripeptidases and proline specific peptidases is presented in addition to the illuminating research which has been performed on the transport systems for peptides and amino acids in lactic acid bacteria. (C) 1997 Elsevier Science Ltd.