Bioactive peptides are fragments of precursor inactive proteins that show specific biological activities and stimulates body functions when specific proteolytic enzymes cleave and modify them into biologically active peptides. bioactive peptides may have some hormone- or drug-like singling properties due to which they act as regulatory products of inactive parent proteins and may influence the physiological activities of the body and may trigger some specific physiological responses.
Sources of Biologically active peptides
Bioactive peptides are immensely found in food derived from various sources. Some common sources of biologically active bio peptides are listed below.
1- Fungi
Some endophytic fungi are found producing valuable bioactive compounds. These compounds have some nutraceutical, therapeutic and pharmacological properties. It is seen that bioactive peptide products of these fungi are helpful to cure many heart and liver diseases. So researchers are investigating bioactive properties of other fungal species for medicinal and phrenological purposes.
2- Plants
A wide range of terrestrial and aquatic plants are known for their bioactive products that contain biologically active peptides that have effective signaling effects on various physiological functions and immunomodulatory responses. Cereals, legumes, beans and other plant products contain biologically active peptides that have enough therapeutic and pharmacological potential to regulate and induce various physiological responses including antioxidant, antihypertensive, antimicrobial and immunoregulatory effects. Some aquatic species are seen enriched with bioactive products that release anticancer peptides.
3- Animals
Various Bioactive peptides containing potential therapeutic and pharmacological potential have been extracted from various terrestrial and marine animal products. Biologically active peptides derived from milk and other dairy products of animals have nutraceutical as well as signaling properties that modulate various physiological responses including immunology of body of the organism. Honey is long been used to cure many diseases due to potential bioactive peptides it contains. Animal species that release venom during metabolic reactions also contain bioactive peptides that are potent pharmacological and therapeutic agents. These active peptides have antimicrobial, antihypertensive and anticancer potentials. Reptilian venom contains bioactive peptides that have anticancer bioactivity.
Extraction of Bioactive Peptides from Food Products:
Biologically active peptides are extracted from precursor proteins derived from food products inside the body during gastrointestinal digestion in two ways.
1- Enzymatic Hydrolysis
During the digestion process, enzymes released by digestive tract cleave inactive precursor proteins and release active fragments of bioactive peptides. Hydrolytic enzymes of gastric tract including pepsin, trypsin, alcalase, chymotrypsin, thermolysin, pancreatin extract biologically active peptides from food proteins by their proteolytic activity.
Intestinal bacteria also release an enzyme that results in fragmentation of food proteins
Into bioactive peptides.
In vitro, various proteolytic enzymes from recombinant DNA technology have been designed for commercial extraction of desired bioactive peptides from proteins derived from food.
2- Microbial Fermentation
In vitro, proteins of dairy products can be fermented by employing bacteria and yeast to extract biologically active biopeptides. These microbes release intracellular proteolytic enzymes mainly proteases and peptidases. Microbial enzymes endopeptidases, aminopeptidases, tripeptidases, and dipeptidases are employed for commercial extraction of peptides that have antihypertensive, immunostimulatory and antioxidative bioactivity.
Types of Bioactive Peptides
Types of bioactive peptides according to their bioactivities.
1- Anti-Oxidative Bioactive Peptides
In all living organisms, reactive oxygen species are produced that may damage tissues of the organism by oxidation reactions. Reactive oxygen species produce free radicles and lipid radicles that cause various health issues.
Different foods have proteins that contain bioactive fragments against oxidation. aromatic amino acids and histidine present in peptides attribute their anti-oxidant property. These anti-oxidant peptides neutralize reactive oxygen species produced during metabolism by donating hydrogen to free radicles and stabilize body lipids and other compounds from oxidation. This anti-oxidant property of bioactive peptides help in the stability of health of an organism and regulate digestive, respiratory and circulatory systems of the body.
2- Antimicrobial Bioactive peptides
Antimicrobial peptides have immense pharmaceutical importance due to their therapeutic potential against pathogens. these peptides are broad spectrum and effective antibiotics with a short chain and positively charged amino acid containing bioactive peptides that can easily be assimilated in body tissues. Bioactive peptides that have antimicrobial bioactivity influence innate immunity and regulate host defense mechanism.
Due to their pharmacological potential, antimicrobial bioactive peptides are employed to resist various bacterial, viral and fungal infections. Antimicrobial peptides have usually cationic properties due to which they specifically target bacterial cytoplasmic membranes and evade and kill them during injury and infection. These peptides restrict pathogen attack by limiting metal ion accessibility to microbes.
These peptides have a direct modulatory effect on the immune system as they influence neutrophils and leukocytes. These peptides also regulatthe e healing process after injury by influencing the transport of monocytes to the site of injury.
3- Anti-Hypertensive Peptides
Lethal Cardiac diseases like heart stroke, coronary heart disease, and heart failure are indirectly caused by physiological hypertension. Heart diseases, abnormal blood pressure, and hypertension are correlated. Food derives bioactive peptides that have anti-hypertensive therapeutic potential are used as substituent pharmacological treatment of hypertension to avoid both mild and acute heart illnesses.
Bioactive peptides with antihypertensive bioactivity are mostly hydrophobic peptides and have aliphatic and aromatic amino acid residues at penultimate positions. These peptides are mostly found in the form of tripeptides. Anti-hypertensive bioactivity of these peptides is associated with their hydrophobic character.
These peptides are also responsible for the regulation of aldosterone which predicts its clinical and pharmacological potential.
4- Immunomodulatory Peptides
Food derived immunomodulatory peptides directly influence the innate immunity of the organism. They play important role in proliferation of leukocytes during infection, activate defense system of the body and influence the production of antibodies against any foreign invader. These immunostimulatory peptides modulate and regulate the phagocytic activity of macrophages.
5- Anti-Cancer Bioactive Peptides
Some biologically active peptides have potential anticancer bioactivity. These bioactive peptides pose inhibitory priorities for angiotensin-converting enzyme and proliferation of abnormally developed cells. These bioactive peptides have cytotoxicity for cancerous cells. These antitumor bioactive peptides promote and induce apoptosis, inhibit angiogenesis of cancer cells and modulate inflammatory responses.
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