Bioactive peptides are small protein fragments that promote metabolic health by exerting a positive influence on biological responses within the body.
The therapeutic applications of these novel molecules include, but are not limited to, anti-oxidant, anti-inflammatory, anti-microbial, and anti-viral activities. They have also been used to treat metabolic disorders, such as Type-2 diabetes and obesity.
Source and Production of Bioactive Peptides
Sources of bioactive peptides include yogurt, milk, cheese, plants, marine organisms, and human saliva. The methods used to produce bioactive peptides are discussed below:
Enzymatic Hydrolysis
A pure form of proteolytic enzyme is used to hydrolyze the protein to produce short peptide sequences. Low molecular weight peptides (<10 kDa) are effective anti-hypertensive, anti-oxidative agents that find commercial application to produce peptides in bulk than high molecular weight peptides.
Microbial Fermentation
Protein is hydrolyzed by culturing bacteria or yeast on the protein substrates. These bacteria or yeast secrete their proteolytic enzymes in due course to release peptides from the proteins.
Each protein hydrolysate differs in their degree of proteolysis. For example, Lactobacillus brevis strain has a strong angiotensin-converting enzyme (ACE) inhibitory activity compared to other lactobacillus strains.
Pharmacological Properties of Bioactive Peptides
The type of N- and C-terminal amino acid, the peptide chain length, charge character, and composition of the amino acids determines the biological activity of bioactive peptides.
For example, opioid peptides are short amino acid sequences with similar pharmacological activity as opium. Typical opioid peptides have the same N-terminal sequence of Tyr-Gly-Gly-Phe, while atypical opioid peptides have varying amino acid sequences at their N-terminal region with conserved tyrosine residue. The tyrosine residue is an important structural motif that is required for the opioid peptide to bind with its corresponding receptor.
Food Peptidomics
This sub-field of proteomics involves developing novel bioactive peptides and generation of peptide databases for industries that produce dairy products. Peptidomics makes use of high-resolution techniques, such as mass spectrometry and chromatography that enables improved and continuous monitoring of food safety and quality.
Therapeutic Applications of Marine-Derived Bioactive Peptides
Marine-derived bioactive peptides, such as jellyfish collagen peptides, protein hydrolysates from muscles of goby fish and sardines are used for their hypotensive, anti-diabetic, hypolipidemic, and hypocholesterolemic activities.
Marine peptides also have skin protection and wound healing properties. Single-blind case-control studies have demonstrated that marine collagen peptides improve skin elasticity and sebum production in healthy participants.
Milk-Derived Bioactive Peptides
Milk-derived bioactive peptides also exert multiple therapeutic functions, such as immunomodulatory, anti-oxidant, anti-microbial, and antagonistic activities against toxic agents. Studies show that properties of these peptides (derived from cow, goat, sheep, buffalo, and camel milk) make them prophylactic agents against cancer, osteoporosis, hypertension, and many metabolic disorders. Some bioactive peptides such as those extracted from Canastra artisanal Minas cheese have been studied extensively for its potent antimicrobial activity against Escherichia coli.
Proteolytic Cleavage of Human Salivary Proteins
Human salivary proteins, including statherin, histatin 3, histatin 1, proline-rich proteins and musin 7 can generate bioactive peptides with anti-microbial, anti-viral, and other therapeutic activities.
Plastein
Plastein is a protease-induced peptide. Recent research has indicated that plastein can increase the nutritional value of low-quality proteins and promote health. They also exert antihypertensive, antioxidative, and antithrombotic activities. An advantage of plastein is that it is stable over a wide range of pH and temperature enabling its use in a variety of food formulations.
The use of nanoparticles for oral delivery of bioactive peptides
Oral nanoparticle formulations increase bioavailability of bioactive proteins and peptides, and improve treatment compliance in the long run. By enhancing the mucoadhesive property of nanoparticles, bioactive peptides can readily reach the blood stream for its intended therapeutic action. Incorporation of bioactive peptides into liposomes via cell-free protein synthesis is another way to develop proteoliposomal nanodelivery systems. For example, cytotoxic peptides such as KLAK are conjugated onto dendrimers (polymeric materials with nanometer-scale dimensions) to enhance intracellular delivery and deep tumor penetration capacity.
With increasing consumer awareness on the health-promoting effects of nutraceuticals, it is imperative to conduct robust clinical trials to provide enough evidence to show that bioactive peptides are useful functional agents to prevent and treat diseases.
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Further Reading