Isolation and identification of the angiotensin-I converting enzyme (ACE) inhibitory peptides derived from cottonseed protein: optimization of hydrolysis conditions

ABSTRACT

Peptides derived from food proteins have exhibited significant antihypertensive effects without side effects. In this study, the cottonseed protein was hydrolyzed by papain for preparing peptide with angiotensin I converting enzyme (ACE) inhibitory activity. The influence of hydrolysis temperature (33°C, 40°C, and 47°C), pH (6.5, 7.0, and 7.5), and enzyme to substrate (E/S) ratio (0.9%, 1.2%, and 1.5%) on the degree of hydrolysis (DH) and ACE-inhibitory activity were analyzed. The hydrolysis conditions were further optimized by central composite design (CCD) and response surface methodology (RSM). The DH of cottonseed protein and ACE inhibitory rate of hydrolysates reached 25.7% and 88.2%, respectively, under the optimal hydrolysis conditions (hydrolysis temperature 39°C, pH 7.5, and E/S ratio 1.04%). We further separated the cottonseed protein hydrolysates (CPH) using a combined strategy of ultrafiltration membrane bioreactor system, sephadex G-25 gel filtration chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). An ACE inhibitory peptide, named as FII-2-P, with ACE inhibitory IC₅₀ value of 46.7 μg/mL, was obtained. MALDI-TOF-TOF mass spectrometry analysis revealed that the molecular weight of FII-2-P was 763.4 Da and its amino acids sequence was Phe-Pro-Ala-Ile-Gly-Met-Lys. These results demonstrated that the cottonseed protein is a potential source of ACE inhibitory ingredients to be used in the development of functional foods.

KEYWORDS:

• Cottonseed protein
• hydrolysis
• ACE inhibitory peptides
• purification and identification
• response surface methodology

Declaration of interest

The authors declare that there is no conflict of interest.

Additional information

Funding

This work was supported by the Ministry of Science and Technology Program of China (NO. KY201501005), the Fundamental Research Funds for the Central Universities of Northwest Minzu University (NO. 31920190023 and 31920190202-04), the Changjiang Scholars and Innovative Research Team in University (NO. IRTIRT_17R88), National Natural Science Foundation of China (NO. 31360375), and Natural Science Foundation of Gansu Province (NO. 18JR3RA368).