Short communication: Inhibition of angiotensin 1-converting enzyme by peptides derived from variants of bovine β-casein upon apical exposure to a Caco-2 cell monolayer

Publication date: Available online 14 December 2016
Source:Journal of Dairy Science
Author(s): Bjørn Petrat-Melin, Thao T. Le, Hanne S. Møller, Lotte B. Larsen, Jette F. Young
This study investigated the consequence of genetically contingent AA substitutions in bovine β-casein (CN) genetic variants A¹, A², B, and I on the structure and bioactive potential of peptides following in vitro digestion. The β-CN variants were digested in vitro using pepsin and pancreatin, and a peptide profile was obtained by liquid chromatography tandem mass spectrometry, revealing among others, the β-casomorphin precursor peptides VYPFPGPIHN and VYPFPGPIPN, derived from variant A¹/B and from A²/I, respectively. These 2 peptides were synthesized and assessed for angiotensin 1-converting enzyme (ACE) inhibitory capacity before and after incubation with a monolayer of Caco-2 intestinal cells. The VYPFPGPIHN was a stronger ACE inhibitor than VYPFPGPIPN, with the concentration needed to reach half-maximal inhibition (IC50) of 123 ± 14.2 µM versus 656 ± 7.6 µM. Exposure to a Caco-2 intestinal cell monolayer did not affect ACE inhibition by VYPFPGPIHN, but resulted in an almost 2-fold increase in inhibition by VYPFPGPIPN after incubation. Subsequent tandem mass spectrometric analysis identified the truncated peptide VYPFPGPIP, suggesting hydrolysis by a cell membrane associated peptidase. Thus, genetic variation in bovine β-CN results in the generation of peptides that differ in bioactivity, and are differently affected by intestinal brush border peptidases.



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