Evaluation of angiotensin I-converting enzyme (ACE) inhibitory activities of smooth hound (Mustelus mustelus) muscle protein hydrolysates generated by gastrointestinal proteases: identification of the most potent active peptide

摘要

In this study, smooth hound protein hydrolysates (SHPHs), obtained by treatment with various gastrointestinal proteases, were analyzed for their angiotensin I-converting enzyme (ACE) inhibitory activities. Protein hydrolysates were obtained by treatment with crude alkaline enzyme extract, low molecular weight (LMW) alkaline protease, trypsin-like protease and pepsin from Mustelus mustelus, and bovine trypsin. All hydrolysates exhibited inhibitory activity toward ACE. Hydrolysate generated with alkaline protease extract displayed the highest ACE inhibitory activity, and the higher inhibition activity (82.6% at 2 mg/mL) was obtained with a hydrolysis degree of 18.8%. This hydrolysate was then fractionated by size exclusion chromatography on a Sephadex G-25 into five major fractions (P-P). ACE inhibitory activities of all fractions were assayed, and P was found to display a high ACE inhibitory activity (62.24% at 1 mg/mL). P was then fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and ten fractions of ACE inhibitors were found (F-F). Sub-fraction F showed the strongest ACE inhibitory activity, being able to suppress more than 60% of initial enzyme activity at a concentration of 100 og/mL. The amino acid sequence of peptide F was determined by ESI/MS and ESI-MS/MS as Ala-Gly-Ser, and the IC value for ACE inhibitory activity was 0.13 pl 0.03 mg/mL. Further, purified peptide F maintained inhibitory activity even after in vitro digestion with gastrointestinal proteases in order to demonstrate gastrointestinal stability digestion to enable oral application. These results indicate that smooth hound protein hydrolysate possesses potent antihypertensive activity.