Proteolytic enzymes and their natural antagonists, the protease inhibitor pro teins, play a crucial role in the physiology and pathology of living organisms including humans. Remark able advantages revealed their wide functional context. Proteases digest food proteinase in the digestive tract and liberate poly peptide hormones, stimulating gastric and pancreatic secretion. Proteases are involved during fertilization in sperm - egg interaction, ovulation, ovum implantation and parturition. Proteases of the renin-angiotensin and kallikrein-kinin systems act synergistically to generate blood...