Milk derived bioactive peptides and its importance in human health
Authors: Apurva Sharma and Chaudhary Madhabahi B
ICAR-National Dairy Research Institute

Bioactive peptides are break down products of protein by protease present in gastrointestinal tract. It has specific functions only after release from parent protein sources.

Production of bioactive peptides

The common methods for generation of bioactive peptides are:

  • Enzymatic hydrolyses of food proteins during digestion of food.
  • Microbial activity in fermented foods.
  • Processing of foods using heat/acid/alkali conditions that hydrolyse protein.

These methods release short chain peptide sequences from intact proteins. Bioactive peptides usually contain 3-20 amino acid residues per molecule. In order to elicit a biological response the peptide must cross the intestinal epithelium and enter blood circulation or bind to specific epithelial cells surface sites.

Important functions of bioactive peptides:

  • Immune-modulating function : Immunomodulation means stimulation of immune system, which stimulates the proliferation of human lymphocytes, phagocytic activity of macrophages. Alleviate allergic reactions in human and enhance mucosal immunity in gastrointestinal tract. Milk protein derived peptides are known to have an effect on cells immune system as well as downstream immunological response and cellular functions.
  • Antioxidant activity : Oxidative metabolism is essential for survival of the cells. A side effect of this process is the production of free radicals and reactive oxygen species. Free radicals over whelm the protective enzymes like superoxide-dismutase, catalase and peroxidase. Bioactive peptides quench the free radicals by oxidation of amino acids. Casein and whey protein hydrolysates with glutamic acid and leucine residues exhibit superoxide radical scavenging activity.
  • Mineral binding ability : Bioactive peptides generated by caseins and whey proteins (ß-lactoglobulin, α lactalbumin) shows mineral binding property through phosphoseryl and carboxyl groups in caseins and peptides from whey proteins binds mineral through glutamic acid and aspartic acid. Cleavage of casein with trypsin enzyme results formation of single and multiple phsphoseryl residues which efficiently binds the calcium, iron, manganese and copper element. Peptides also play a crucial role in protecting milk gland against calcification by controlling the calcium phosphate precipitation.
  • Antimicrobial activity : antimicrobial activity of milk is mainly associated with whey protein primarily lactoferrin because its ability to bind iron and to deprive micro-organisms of this essential nutrients. However, hydrolysis of lactoferrin by pepsin produces hydrolysates in which antimicrobial potency is higher than that of undigested lactoferrin. These peptides have antimicrobial activity against gram positive, gram negative bacteria, yeast, fungi and virus.
  • ACE inhibitory activity : Angiotensin is a blood polypeptide. Inactive angiotensin-I converts into active angiotensin-II by ACE (Angiotensin-I converting enzyme). Active angiotensin stimulates the release of aldosterone from adrenal cortex, which causes vasoconstriction and subsequent increase in blood pressure. Some peptides derived from casein and whey protein possesses inhibitory activity against ACE, thereby decreasing blood pressure. Peptide (lactokinins) produce from whey proteins like ß-lactoglobulin, α lactalbumin and blood serum albumin shows ACE inhibitory activity.
  • Anti-thrombin activity : Thrombosis is formation of blood clot inside a blood vessel and obstructing the flow of blood circulation system. Milk derived peptides are known to inhibit platelets. Hydrolysis of bovine k-casein by chymosin gives N-Terminal para-K-casein and C-terminal caseino-macropeptides. Further hydrolysis of caseino-macropeptides by trypsin or chymotrypsin produce a series of peptides collectively known as casoplatelin and it shows anti-thrombin activity.

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