MILK PROTEIN DERIVED BIO ACTIVE PEPTIDES.pptx

Bioactive peptides present in milk are inactive in their native state. milk has numerous bioactive compounds such as proteins, lipids, vitamins, lactose and minerals. They are released during hydrolysis of digestive enzymes or hydrolysis of proteolytic microoraganisms or hydrolysis of proteolytic enzymes from plant.

1. MILK PROTEIN DERIVED BIOACTIVE PEPTITEDS -THEIR PROPERTIES; SIGNIFICANCE AND APPLICATION; BITTER PEPTIDES IN CHEESE; GROWTH FACTORS IN MILK KARTHIKA R PHD DAIRY CHEMISTRY

2. MILK PROTEIN DERIVED BIOACTIVE PEPTITEDS Bioactive peptides are present in an inactive state in their native protein molecules and are liberated by (1) Gut microbial enzymes (2) gastrointestinal enzymes (3) milk-derived proteases  (4) microorganisms secreting enzymes (used as starter cultures) which are then added during the processing of milk (Park & Nam, 2015).

3. Bioactivity of milk components have been categorized as four major areas: gastrointestinal development, activity, and function; (2) immunological development and function; (3) infant development; and (4) microbial activity, including antibiotic and probiotic action Gobbetti  et al., 2007

4. Park, 2009b

5. BPs have been defined as specific protein fragments that have a positive influence on physiological and metabolic functions or condition of the body. Most of the bioactivities of milk proteins are being absent or incomplete in the original native state. BPs are inactive within the sequence of the parent protein, and they can be released in three ways: ( i ) through hydrolysis by digestive enzymes , (ii) through hydrolysis of proteins by proteolytic microorganisms , and (iii) through the action of proteolytic enzymes derived from plants 

6. Antihypertensive peptides The angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin-angitensin system, which regulates blood pressure. The ACE causes elevation of blood pressure by converting angiotensin -I to the angiotensin -II. The ACE-inhibitors derived from milk proteins are attributed to different fragments of casein, named casokinins , or whey proteins, named lactokinins .

7. Milk protein-derived antihypertensive peptides which act as angiotensin I-converting enzyme inhibitors (CEI)

8. Antioxidative peptides Peptides derived from α s-casein have free radical-scavenging activity and inhibit enzymatic and nonenzymatic lipid peroxidation . Proteolytic enzymes can release antioxidative peptides from caseins, soybean and gelatine by enzymatic hydrolysis . Low temperature-processed whey protein contained high levels of specific dipeptides ( glutamylcysteine ).These dipeptides can promote the synthesis of glutathione , which is an important antioxidant for cellular protection and repair processes. Antioxidant activities of hydrolysates were evaluated using DPPH radical scavenging activity.

9. Antithrombotic peptides These peptides reduce or inhibit the formation of blood clots . Caseinomacropeptide (CMP) is a peptide split from k-casein when the milk protein is coagulated by rennin enzyme. This CMP has functions of inhibiting the aggregation of blood platelets and binding of the human fibrinogen. There are two reported antithrombotic peptides , derived from human and bovine k- caseinoglycopeptides , which were identified in the plasma of 5-d-old newborns after breast-feeding and feeding cow milk based formula.

10. Hypocholesterolemic peptides A novel peptide (Ile-Ile-Ala- Glu -Lys ) from tryptichydrolysate of β- lactoglobulin showed hypocholesterolemic effect. Antiappetizing peptides These peptides have functions of suppressing the appetite , whereby they prevent gaining weight and obesity. Total whey protein in the diet has been associated with a lowering of LDL cholesterol, and also related to the increased release of an appetite-suppressing hormone, cholecystokinin Immunomodulatory peptides Immunomodulatory peptides generated from milk include α s1 -CN f194-199 ( α s1 -immunocasokinin) and β- CN f193-202, f63-68, f191-193 ( immunopeptides ), which are synthesized by hydrolysis with pepsin- chymosin .

11. Opioid peptides An opioid is any chemical such as morphine that resembles opiates in its pharmacological effects. Opioid peptides are opioid receptor ligands with agonistic or antagonistic activities . The α s1 -casein-exorphin ( α s1 -CN f90-96), β- casomorphins-7 and -5 ( β- CN f60-66 and f60-64, respectively), and lactorphins ( α- lactalbumin f50-53 and β- lactoglobulin f102-105) act as opioid agonists . whereas casoxins (i.e., k-CN f35-42, f58-61, and f25-34) act as opioid antagonists . The hydrolysis of  Lactobacillus fermented UHT milk by the pepsin/ trypsin has shown to release several opioid peptides from α s1 - and β- CN, and α- lactalbumin .

12. Antimicrobial peptides Among antimicrobial peptides, the lactoferricins are studied the most, which are derived from bovine and human lactoferrin . Lactoferricins have been shown to have antimicrobial activity against various Gram-positive and -negative bacteria, yeasts and filamentous fungi. Lactoferricin is an amphipathic , cationic peptide with anti-microbial and anti-cancer properties. Lactoferricin can be generated by the pepsin-mediated digestion of lactoferrin .

13. Lactenin may have been the first antibacterial factor found in milk, which has been released from rennet hydrolysis of milk. Casecidins are a group of basic, glycosylated and high molecular weight (about 5 kDa ) polypeptides, which possess bactericidal properties against lactobacilli and also against various pathogenic bacteria such as  Staphylococcus aureus . Isracidin is another antibacterial peptide derived from α s1 -CN , which is hydrolyzed with chymosin .

14. Mineral binding peptides Mineral-binding phosphopeptides or caseinophosphopeptides (CCPs) have the function of carriers for different minerals by forming soluble organophosphate salts, especially Ca++ ion. About 1 mol of CPP can bind 40 mol of Ca 2+ . The α s1 -, α s2 - and β-CN of cow milk contain phosphorylated regions which can be released by digestive enzymes. Specific CPPs can form soluble organophosphate salt and increase Ca absorption by limiting Ca precipitation in the ileum. The negatively charged side chains, particularly the phosphate groups, of these amino acids of CPPs become the specific binding sites for minerals. Chemical phosphorylation of α s1 - and β-CN increased the binding capacity and the stability of these proteins in the presence of Ca 2+

15. Schanbacher   et al . (1998), Meisel (1998), and Clare and Swaisgood (2000), Park (2009b)

16. MARCONE et al., 2017.

17. APPLICATION:

18. GROWTH FACTORS IN MILK Many growth factors in milk have been identified, such as Epidermal growth factors (EGF), Colony - stimulating factors Insulin-like growth factor (IGF), Transforming like growth factors (TGF), Mammary derived growth factors (MDGF), Platelet-derived growth factors (PDGF), basic fibroblast growth factors ( bFGF ) Lactulose from lactose, Nucleotides, Somatotropin

19. The term 'growth factor' is applied to a group of potent hormone-like polypeptides which play a critical role in the regulation and differentiation of a variety of cells acting through cell membrane receptors. Quantitatively, the relative concentrations of growth factors in milk are IGF-I > TGF- β2 > EGF ≈ IGF-II > bFGF . The concentrations of growth factors are highest in colostrum and gradually decrease through lactation, except for BTC ( betacellulin ) .

20. EGF and BTC stimulate proliferation of epidermal, epithelial and embryonic cells, inhibit the secretion of gastric acid and promote wound healing and bone reabsorption while TGF- βs are important in embryogenesis, tissue repair and control of immunity. IGF-I and II are important for cell proliferation ( reproduction of new parts or cells). The role of EGF, IGFs-I and II, insulin and TGF-β in stimulating GI tissue growth and repair in the suckling neonate. PDGF growth factors are involved in embryonic development and proliferation of many cell types. FGF is important for the proliferation and differentiation of epithelial, endothelial and fibroblast cell, promote collagen synthesis and are involved in angiogenesis and wound healing.

21. Bovine mammary secretions contain many compounds that stimulate the growth of cells in cultures : 1. IGFs , part of the insulin family which includes insulin, IGF-I, IGF-II and relaxin . IGFs act as mediators of growth, development and differentiation. They are heat and acid-stable and hence have potential bioactivity in the GIT of consumers. 2. Insulin occurs in bovine milk and colostrum at much higher concentrations than in blood and higher in turn in pre partum secretions than in those post partum. 3. Transforming growth factors (TGF α and β ), are present in bovine milk. TGF-β is important for cell proliferation and differentiation.

22. Human milk contains physiologically active levels of growth factor, whereas bovine milk has much lower levels of growth factor activity. Colostrum of most mammals usually contains high concentrations of growth factors and others bioactive compounds, while the high levels of these growth factor compounds drop rapidly during the first 3 d postpartum . Goat milk is shown to be a great source of physiologically active growth factors. Caprine milk has yet to be studied in this premise .

23. BITTER PEPTIDES IN CHEESE; Bitterness is a common flavor attribute of aged cheese associated with the peptide fraction , but excessive levels are a defect leading to consumer rejection. Known bitter peptides in cheese are derived from the breakdown of αs1-, αs2-, β- and κ-casein due to enzymatic hydrolysis from rennet. Some studies have indicated that αs1-casein is the primary source of bitter peptides in cheese, whereas others have indicated that β-casein is the primary source of bitter peptides Compared with αs1-casein and β-casein, αs2-casein, κ-casein and whey proteins are rarely referenced in the literature as sources of bitter peptides The cause of a peptide’s bitterness has been linked to physical properties, including hydrophobicity , molecular weight, peptide length and amino acid (AA) composition .

24. Factors that affect bitterness in cheese Bitterness in cheese has been linked to many factors in the cheese making process, Initial milk quality, pH, Fat, Salt ( NaCl ) and Cheese mineral content (MgCl2 and CaCl2); Quantity and type of bacterial cultures and rennet applied, The degree of sanitation used in processing and packaging conditions

25. Reduced pH in milk is often linked to poor milk quality and has been associated with the formation of bitter flavor in cheese. Cheeses with lower fat have a higher tendency of being bitter. Low salt concentrations in cheese are associated with bitterness . A more recent analysis indicated that the presence of MgCl2 and CaCl2 are critical for the perception of bitterness for peptides and amino acids in aged gouda cheese

26. Excessive action of rennet or rennet substitutes (either via excess addition to milk or prolonged exposure to rennet) can lead to overproduction of bitter peptides. Hydrolysis of casein by rennet releases large peptides that may not initially be bitter but can become precursors to bitter peptides through additional proteolytic cleavage. Proteolytic starter bacteria, such as Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris , have high proteolytic activity - can cause the formation of bitter peptides. Nonstarter bacteria can also produce proteases that can hydrolyze milk proteins and produce bitter peptides. Endogenous milk proteinases , such as plasmin , can act on proteins during cheese making and contribute to bitterness. Plasmin is resistant to high temperatures and survives pasteurization, which enables it to remain active during cheese making.

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