3. Bioactive Peptides

Peptides are low molecular weight fragments of proteins, usually with sizes not exceeding 20 kDa. Bioactive peptides are those that can have a positive influence on human through modulation of various physiological processes. Peptides are produced by in vitro digestion with suitable proteases to give a protein hydrolysate or through protein fermentation with suitable microorganisms; the protein hydrolysates and fermented products contain peptides that differ in structural and functional characteristics. Peptides are susceptible to rapid structural breakdown in the body, and therefore, bioactive properties require resistance to enzymatic hydrolysis (true inhibitor) or conversion into active products when acted upon by proteolytic enzymes (pro-drug). Antihypertensive peptides are the most researched of all the bioactive peptides, and their action involves inhibition of angiotensin- converting enzyme (ACE) activity, one of the key enzymes that control the renin-angiotensin system. The ACE-inhibiting peptides have been shown to reduce blood pressure in rats and humans. Other bioactive peptides include those that bind to calmodulin (CaM) and reduce activation of CaM-dependent enzymes that are implicated in the pathogenesis of chronic diseases. Antioxidant peptides have the ability to donate electrons and bind metal cations, which suppress the toxic effects of free radicals, prevent lipid peroxide formation, and protect DNA from oxidative damage. Peptides also have anti-inflammatory and immunomodulatory effects as exhibited through enhanced cellular production of protective cytokines; therefore, these peptides have been suggested to have potential role in cancer prevention.