The physiological roles of bioactive peptides are categorised into five distinct groups. A living system responds to the amino acid sequences in these molecules. Scientists have mapped most known bioactive peptides into these primary classifications. bluumpeptides.com maintains detailed catalogues of peptide families and their documented biological effects. Each category operates through distinct mechanisms and shows different therapeutic possibilities. Grasping these classifications reveals how peptides act as biological regulators.
Antimicrobial peptides function
Ancient immune defense molecules, antimicrobial peptides appear across all kingdoms of life. Human skin alone secretes over twenty distinct varieties continuously. Membrane disruption kills bacteria rather than metabolic interference. Positively charged peptides get attracted to negatively charged bacterial membranes through electrostatic forces. Between 29 and 45 amino acids make up defensins, which have characteristic beta-sheet structures. Their three-dimensional shape stays stable through six disulfide bonds. During the digestive process, neutrophils and Paneth cells produce alpha-defensins. Epithelial tissues, such as the airways and urogenital tract, contain beta-defensins predominantly. Both subtypes punch lethal pores after inserting into bacterial membranes.
Antioxidant peptides protect
The cellular neutralisation capacity becomes overwhelmed when reactive oxygen species accumulate. Antioxidant peptides correct this imbalance by transferring electrons and chelating metals. The amino acid makeup determines the potency of the antioxidant effect. Particularly potent antioxidant peptides come from marine sources:
- Leu-Ser-Gly-Tyr-Gly-Pro from tuna dark muscle shows strong radical scavenging
- Gly-Pro-Hyp sequences get released from salmon skin collagen through enzymatic hydrolysis
- Cys-Gly-Phe peptides from oyster protein demonstrate metal chelation properties
- Glu-Cys-Gly tripeptides in algae proteins mimic glutathione
Specific proteases, operating at controlled pH and temperature, enable efficient industrial extraction.
Opioid peptides modulate
Proenkephalin cleavage produces enkephalins. Only the C-terminal amino acid differs between Met-enkephalin and Leu-enkephalin. Both pentapeptides favour Delta receptors. Prodynorphin generates dynorphins, which preferentially activate kappa receptors. Dynorphin A holds 17 amino acids; dynorphin B has 13. Gastrointestinal digestion releases exogenous opioid peptides from proteins in food. Casomorphins come from casein, particularly beta-casomorphin-7 from A1 beta-casein. Wheat gluten produces gluten exorphins. Hemoglobin creates hemorphins.
Immunomodulating peptides regulate
Cytokines coordinate receptor-mediated signalling cascades during immune responses. The interleukin family comprises over 40 members. T-cell proliferation gets activated by IL-2. IL-4 regulates B-cell differentiation and antibody class switching. Inflammatory responses are suppressed through IL-10. Specific structural domains in each cytokine determine receptor binding specificity.
Chronic hepatitis B treatment and immune enhancement during chemotherapy represent clinical applications. An 80-kilodalton iron-binding glycoprotein called lactoferrin is digested to produce immune modulating peptides:
- Residues 17-41 form lactoferricin, which demonstrates antimicrobial properties
- Residues 268-284 make lactoferrampin with both antimicrobial and immunomodulatory effects
- These fragments stimulate mast cell phagocytosis and natural killer cell activity
Bovine colostrum reaches particularly high lactoferrin concentrations at 1-2 grams per liter. Mature milk contains only 0.1-0.3 grams per liter by comparison.
Enzyme inhibitor peptides
The conversion of angiotensin I to the vasoconstrictive angiotensin II is prevented by angiotensin-converting enzyme inhibitors. Hydrolysis of multiple food sources yields ACE-inhibitory peptides. Sardine muscle produces Val-Tyr with an IC50 of 1.2 micromolar. Bonito bowels contain Leu-Lys-Pro-Asn-Met, which gets marketed commercially as a functional food ingredient in Japan. Casein produces the tripeptide Ile-Pro-Pro, which demonstrates ACE inhibition at an IC50 of 5 micromolar. Peptide transporters in the intestinal epithelium handle its absorption. Following dietary intake, plasma concentrations reach 10-20 nanomolar. Several weeks of consumption produce modest blood pressure reductions of 5-10 mmHg systolic in human studies.
Incretin hormone degradation is slowed by dipeptidyl peptidase IV inhibitors, which enhance insulin secretion. Milk protein hydrolysates yield Val-Pro and Ile-Pro-Ile with DPPIV inhibitory activity. Fermentation or enzymatic processing also generates DPPIV-inhibitory sequences from soy and wheat proteins.