Preparation and Amino Acid Composition of ACE-inhibitor Peptides in Yinghong Tea Proteins and the Activity of Their Ultrafiltrated Components
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Abstract:
Based on tea proteins extracted from Yinghong No. 9 dregs via alkali extraction and acid precipitation, single-factor and response surface designs were used to optimize the preparation of tea-protein angiotensin-converting enzyme (ACE)-inhibitor peptides and maximize the ACE inhibition rate. Protein hydrolysates were subjected to amino acid composition analysis and ultrafiltration membrane separation, and the ACE inhibitory activity of each ultrafiltrated molecular component was analyzed. Enzymolysis conditions of 37 ℃, 3.20 hours, pH of 7.20, substrate mass concentration of 3%, and enzyme-to-substrate mass ratio of 0.40% were found to be optimal for the preparation of ACE-inhibitor peptides and resulted in ACE-inhibitor peptides with an experimentally measured ACE inhibition rate of 83.38%, which is close to the theoretical value of 84.48%. The obtained tea-protein hydrolysate was rich in essential amino acids (33.03%) and hydrophobic amino acids (47.20%), the latter of which is important for ACE-inhibiting activity. Furthermore, the ACE-inhibitory activity of the <3 ku components obtained from ultrafiltration membrane separation (IC50=0.85 mg/mL) is significantly stronger than that of protein hydrolysate (IC50=1.37 mg/mL) and the >3 ku components (IC50=2.81 mg/mL). The findings of this study are expected to serve as theoretical reference for the research and development of food-derived ACE-inhibitor peptides and the value-added utilization of Yinghong No. 9 tea proteins.
