Optimization of Extraction Process and in Vitro Hypolipidemic Activity of White Kidney Bean Protein Source Lipid-lowering Peptide

This study systematically analyzed white kidney bean proteins to optimize the enzymatic digestion process for the preparation of polypeptides derived from white kidney beans (White kidney bean polypeptides, WKBPs) and to investigate their active lipid-lowering fragments in vitro. The ideal preparation conditions for WKBPs were established using single factor experiments and response surface methodology, while the amino acid composition of white kidney bean protein was thoroughly assessed before and after enzymatic hydrolysis. Crude peptides were subsequently separated using ultrafiltration membranes, and the lipid-lowering effects of the various WKBPs fractions were evaluated, and the binding ability and target of peptide sequences with pancreatic lipase were explored using molecular docking. The optimized conditions for enzymatic hydrolysis were determined to be a temperature of 51 ℃, a duration of 3 hours, an enzyme dosage of 3000 U/g, and a pH of 10.0. Under these circumstances, the WKBPs attained a pancreatic lipase inhibition rate of 83.58%±0.65%. In comparison to the unhydrolyzed white kidney bean protein, the WKBPs demonstrated extremely significant enhancements in essential amino acids (from 31.51±0.22 g/100 g to 35.97±0.06 g/100 g), hydrophobic amino acids (from 29.47±0.25 g/100 g to 34.15±0.11 g/100 g), and total amino acids (from 83.21±0.11 g/100 g to 94.08±0.12 g/100 g) (P<0.01). Ultrafiltration analysis indicated that WKBPs with a molecular weight (Mw) <3000 Da exhibited the most potent in vitro anti-hyperlipidemic activity, with half-maximal inhibitory concentrations of 1.43, 0.28, and 0.90 mg/mL for the inhibition of cholesterol esterase, pancreatic lipase, and sodium taurocholate, respectively. A virtual screening of 2997 peptide sequences, identified via mass spectrometry, demonstrated that the peptide RPPFDPY displayed the lowest binding energy and the highest affinity for pancreatic lipase. Molecular docking simulations indicated that RPPFDPY could establish a stable complex with pancreatic lipase via hydrogen bonding and hydrophobic interactions. This study offers significant theoretical insights and data to facilitate the creation of innovative functional foods derived from bioactive peptides of white kidney beans.