Antibacterial peptides derived from caprine whey proteins, by digestion with human gastrointestinal juice

Abstract

Peptides in caprine whey were identified after in vitro digestion with human gastrointestinal enzymes in order to determine their antibacterial effect. The digestion was performed in two continuing steps using human gastric juice (pH 2·5) and human duodenal juice (pH 8) at 378C. After digestion the hydrolysate was fractionated and 106 peptides were identified. From these results, twenty-two peptides, located in the protein molecules, were synthesised and antibacterial activity examined. Strong activity of the hydrolysates was detected against Escherichia coli K12, Bacillus cereus RT INF01 and Listeria monocytogenes, less activity against Staphylococcus aureus ATCC 25 923 and no effect on Lactobacillus rhamnosus GG. The pure peptides showed less antibacterial effect than the hydrolysates. When comparing the peptide sequences from human gastrointestinal enzymes with previously identified peptides from non-human enzymes, only two peptides, b-lactoglobulin f(92 -100) and b-casein f(191 -205) matched. No peptides corresponded to the antibacterial caprine lactoferricin f(14 -42) or lactoferrampin C f(268 -284). Human gastrointestinal enzymes seem to be more complex and have different cleavage points in their protein chains compared with purified non-human enzymes. Multiple sequence alignment of nineteen peptides showed proline-rich sequences, neighbouring leucines, resulting in a consensus sequence LTPVPELK. In such a way proline and leucine may restrict further proteolytic processing. The present study showed that human gastrointestinal enzymes generated different peptides from caprine whey compared with non-human enzymes and a stronger antibacterial effect of the hydrolysates than the pure peptides was shown. Antimicrobial activity against pathogens but not against probiotics indicate a possible host-protective activity of whey.

Angiotensin I-Converting Enzyme (ACE) Inhibitory Activity and ACE Inhibitory Peptides of Salmon (Salmo salar) Protein Hydrolysates Obtained by Human and Porcine Gastrointestinal Enzymes

“…It is interesting to note that the protein bands corresponding to the apparent molecular mass of actin remained nearly intact for all hydrolysates, suggesting that this subunit is rather stable in the part of the protein and hindered access from gastric juices and pepsin. Similar relations were reported by Eriksen et al [42] who compared the course of in vitro hydrolysis of milk proteins with pepsin with hydrolysis with human gastric juices.…”

Ex vivo digestion of carp muscle tissue – ACE inhibitory and antioxidant activities of the obtained hydrolysates

“…12,13 The results of studies with human digestive enzymes (ex vivo digestion) are closer to the results from in vivo rather than in vitro experiments. These studies have mimicked or approximated the physiological conditions of the human body.…”

Generation of antibacterial peptides from crude cheese whey using pepsin and rennet enzymes at various pH conditions

“…26 Liberation of the three antibacterial peptides from cheese whey by three enzymes at various pHs was examined. LC-MS/MS analysis revealed that -lactoglobulin f(92-103) and lactoferrin f (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) were generated by pepsin-mediated digestion at pH 2.5 and 3.0, whereas -lactoglobulin f (14)(15)(16)(17)(18)(19)(20)(21)(22) was generated only at pH 2.5. In contrast, calf rennet digestion generated the all three peptides at a wider pH range (2.5-3.5) ( Fig.…”