Effect of gallic acid on peptides released by trypsin digestion of bovine α-casein.
J Biosci Bioeng 2012;
115:259-67. [PMID:
23164682 DOI:
10.1016/j.jbiosc.2012.10.003]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/14/2012] [Accepted: 10/01/2012] [Indexed: 11/22/2022]
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.
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