title: Yak milk casein as a functional ingredient: preparation and identification of angiotensin-I-converting enzyme inhibitory peptides.
abstract: Yak milk casein derived from Qula, a traditional Tibetan acid curd cheese, was hydrolyzed by six commercially available proteases (Trypsin, Pepsin, Alcalase, Flavourzyme, Papain and Neutrase). These hydrolysates were assayed for their inhibitory activity of Angiotensin-I-converting enzyme (ACE). The hydrolysates obtained by Neutrase from Bacillus amyloliquefaciens showed the highest ACE inhibitory activity. The IC50 value of Neutrase-hydrolysate was 0.38 mg/ml. The hydrolysate obtained by Neutrase was further separated by consecutive ultra-filtration with 10 kDa and then with 6 kDa molecular weight cut-offs into different permeated parts and fractionated by gel filtration chromatography with a Sephadex G-25 column. The active fraction was subjected to RP-HPLC, in which five peaks were purified and identified. Amino acid sequence analysis confirmed that the peptides and origins were as follows: YQKFPQY (alphas2-CN; f89-95), LPQNIPPL (beta-CN; f70-77), SKVLPVPQK (beta-CN; f168-176), LPYPYY (kappa-CN; f56-61) and FLPYPYY (kappa-CN; f55-61). Their amino acid sequences matched well with those of known bioactive peptides from bovine casein. The results indicated that yak milk casein could be a resource to generate antihypertensive peptides and be used as multifunctional active ingredients for many value-added functional foods as well as a traditional food protein.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China.
authors.forename: Jingli
authors.initials: J
authors.lastname: Jiang
authors.forename: Shangwu
authors.initials: S
authors.lastname: Chen
authors.forename: Fazheng
authors.initials: F
authors.lastname: Ren
authors.forename: Zhang
authors.initials: Z
authors.lastname: Luo
authors.forename: Steve S
authors.initials: SS
authors.lastname: Zeng
mesh_terms: D000595:Amino Acid Sequence; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D000818:Animals; D002364:Caseins / Q000737:chemistry*; D002417:Cattle; D002611:Cheese; D008892:Milk / Q000201:enzymology*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011492:Protein Hydrolysates / Q000737:chemistry / Q000378:metabolism
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002364:Caseins; D010455:Peptides; D011492:Protein Hydrolysates; D007703:Peptidyl-Dipeptidase A