title: Effect of gallic acid on peptides released by trypsin digestion of bovine α-casein.
abstract: In this study, the effects of gallic acid (GA) on trypsin digestion of commercial α-casein (α-CN), which contains α(s1)-CN and α(s2)-CN, and the peptides released during digestion were investigated. Gallic acid showed no effect on the initial rate of digestion. However, the apparent degree of hydrolysis achieved its maximum value after 1 h, then decreased in the presence of GA, suggesting the cross-linking between peptides once released from α-CN during digestion. In the presence of GA, three peaks derived from α(s1)-CN disappeared and three new peaks appeared in high-performance liquid chromatography (HPLC) analysis. In these peptides, two Met residues corresponding to the Met(135) and Met(196) in α(s1)-CN were oxidized to Met sulfoxide residues. The oxidation of Met(196) was quicker than that of Met(135). The inhibitory activity of TTMPLW (α(s1)-CN 193-199) against angiotensin I-converting enzyme was reduced slightly by the oxidation of its Met residue.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Japan.
authors.forename: Ping
authors.initials: P
authors.lastname: Lai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okazawa
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Izumi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Bamba
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Fukusaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yoshikawa
authors.forename: Akio
authors.initials: A
authors.lastname: Kobayashi
mesh_terms: D000595:Amino Acid Sequence; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D005707:Gallic Acid / Q000494:pharmacology*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D014357:Trypsin
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002364:Caseins; D010455:Peptides; D005707:Gallic Acid; D014357:Trypsin