Extraction, Purification and Characterization of a Pure Peptide from Soybean to Demonstrate Anti-Proliferation Activity on Human Cancer Cells and Test the Ability of Soy Peptide Fractions in Reducing the Activity of Angiotensin-I Converting Enzyme

Proteins are of major interest for nutritional value, functionality and sensory characteristics in foods, and biological activity as health-promoting ingredients. A large number of potential biological activities are encrypted within the primary structures of animal and plant proteins. This research has been based on utilizing a legume by-product, soybean meal, to obtain value-added protein products. Forty four Arkansas grown soybean lines were subjected to analysis for protein and amino acid (profile) content to select lines that have high protein attributes. Three soybean lines, R95-1705 (high yielding, non-transgenic and high protein), N98-445A and S03-543CR (bred for high oleic acid - monounsaturated fatty acid) were selected for further study. Seeds from the three soybean lines were ground and defatted to prepare the meals. The protein isolates (SPI) with highest (90-93%) purity prepared from the three meals were hydrolyzed using a food grade enzyme, Alcalase 2.4L, under optimal hydrolysis conditions to prepare protein hydrolysates (pools of peptides). The protein hydrolysates were tested using simulated gastric and intestinal juices to determine the gastro-intestinal (GI) resistance of the peptides. The GI resistant hydrolysates were fractionated to collect distinct molecular size cut-offs of 50kDa using ultra-filtration technique. These peptide fractions were tested for biological activities including inhibition of ACE-I activity and cancer cell proliferation inhibition using specific assays. Research highlights include demonstration of ACE-I activity inhibition and cancer cell anti-proliferation activity by the GI-resistant peptides from the soybean lines in comparison to positive controls, Captopril (anti-hypertensive drug) and Genistein (anti-cancer agent). A comprehensive screening provided definitive selection criteria for choosing the 10-50kDa fraction from N98-4445A for further purification to separate a single pure peptide with enhanced biological activity. A purified peptide with a sequence of 158 amino acids and molecular weight of 18kDa from the 10-50kDa fraction showed nearly 75 and 80% inhibition of blood and colon cancer cells respectively. Hence, the importance of this investigation is in the potential ability of a peptides obtained from soybean meal protein to sustain a progressive impact on human health condition.