The hydrolysis of muscular proteins to peptides is mainly achieved by the activity of endogenous enzymes. The endopeptidases - cathepsins B, B + L and H – ware shown to remain active throughout the fermentation of dry cured ham and fermented sausages, whereas tissular calpains are inactivated during fermentation and do not contribute significantly to overall to overall proteolysis. Furthermore, muscle exopeptidases contribute to peptide conversion amino acids. The proteolytic system of lactobacilli consists mainly of cell wall-associated proteinases, which convert proteins to oligopeptides. Oligoprptide transport is the main route for nitrogen entry into the bacterial cells, and virtually all peptidases are located intracellularly. The proteolytic activity of starter cultures is weak compared to tissue enzymes. Correspondingly,the inoculation of sausage minces with starter cultures leads to only a minor increase in amino acid levels of the sausages compared to aseptic control batches.The proteolytic activity of kocuria varians is inhibited by environmental conditions prevailing during sausage ripening, yet the peptidase activity of this organism may contribute to the formation of amino acids. It was recently shown that Lb. casei utilizes peptides released from pork muscle sarcoplasmic and myofibrillar proteins under conditions of sausage ripening.