Abstract
In this work, we report the potency of enzymatic hydrolysates of pea proteins against trypsin and chymotrypsin. Pea protein concentrate was digested with each of alcalase, chymotrypsin, pepsin, and trypsin, followed by membrane separation of the protein hydrolysates into peptide fractions (<1, 1–3, 3–5, and 5–10 kDa). Peptide size profiling with size-exclusion gel chromatography indicated the narrowest size range (0.85–4.98 kDa) for alcalase. Trypsin activity was strongly (p < 0.05) inhibited by the ultrafiltration fractions (mean IC50 = 2.2 mg/mL) obtained from the trypsin hydrolysate when compared to the unfractionated hydrolysate (IC50 = 6.8 mg/mL). Similarly, ultrafiltration also enhanced trypsin inhibition by the alcalase-digested peptides with an IC50 of 21.4 mg/mL for the unfractionated hydrolysate in comparison to 3.1–4.7 mg/mL for the fractions. However, ultrafiltration did not enhance trypsin inhibitory activity of chymotrypsin-digested peptides, while the peptide separation reduced efficacy of pepsin-digested peptides. In contrast, chymotrypsin inhibition by all the enzymatic digests was significantly (p < 0.05) enhanced by ultrafiltration, especially peptide sizes >3 kDa. Kinetics of enzyme inhibition indicate peptides were bound to the enzyme active site in a competitive mode that led to reduced catalysis. We conclude that the pea peptides could function as useful tools to promote human health and as a preservative during food processing and storage.
Highlights
Food-derived protease inhibitors have essentially been in the form of large proteins that block activities of trypsin and chymotrypsin, the major serine proteases
We report the ability of enzymatic protein hydrolysates to reduce the catalytic rate of trypsin- and chymotrypsin-catalyzed reactions
Ultrafiltration separation of the peptides yielded fractions with stronger inhibitory activity against chymotrypsin while the effect on trypsin inhibition was dependent on type of enzyme used for protein hydrolysis
Summary
Food-derived protease inhibitors have essentially been in the form of large proteins that block activities of trypsin and chymotrypsin, the major serine proteases. The physiological roles of protease inhibitors are diverse and include regulation of various cellular activities, prevention of organ structure deterioration (e.g., the pancreas), and inhibition of viral infections [12]. This is because proteases are involved in the irreversible hydrolysis of peptide bonds; unregulated proteolysis can lead to serious metabolic disorders that precipitate the onset and progression of diseases such as cancer, cardiovascular disorders, neurodegeneration, and chronic inflammation [12,13,14,15,16,17]. Protease inhibitors have been shown to inhibit proliferation of preadipocytes, which suggests an anti-obesity potential [18]
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