Chapter 4.14 - Protein hydrolysates

Abstract

Protein hydrolysates encompass of 2 to 20 amino acid residues (oligopeptides), released by hydrolysis either during gastrointestinal digestion in the body or during fermentation. Generation of bioactive peptides depending on the reaction environment and amino acid residues can either increase or decrease the antioxidant activity of protein hydrolysates. Other than the chemical composition, the hydrophobicity of the hydrolysates affects the antioxidant activity of the bioactive peptides. In assonance, bioactive peptides have antioxidant action as they are capable of scavenging or quenching free radicals and reactive oxygen species (ROS) mainly due to proton-coupled single electron or hydrogen atom transfer mechanism. Furthermore, the antioxidant activities of protein hydrolysates could be increased if there is higher contact of the functional group of the peptides, also, phenolic hydroxyl group present in aromatic amino acids may contribute to scavenge free radical via acting as an electron donor. Moreover, protein hydrolysates have a selective antiproliferative property by augmenting intrinsic apoptosis and blocking the cell cycle in the G1 phase. In addition, protein hydrolysates (Serine-Arginine-Cysteine-Histidine-Valine and Proline-Glutamine-Histidine-Tryptophan) at concentration of up to 300 µg/mL did not exhibit cytotoxicity in HepG2 cells and the level of SOD, CAT and GSH-Px were expressively up-regulated in a dose-dependent manner, however, protein hydrolysates can be deleterious in cancer patients through the ROS-p53 axis. Due to insufficient data from human studies and the data from in vitro and in vivo cannot be extrapolate to humans due to variability, hence, health benefits claim should not be made.