Identification and synthesis of multifunctional peptides from wheat germ hydrolysate fractions obtained by proteinase K digestion.

Abstract

Wheat germ protein hydrolysate (WGPH) was obtained by proteinase K digestion, in order to produce bioactive antioxidant and antihypertensive peptides. Response surface methodology (RSM) was used to optimize hydrolysis conditions (enzyme-to-substrate ratio, time, and temperature) for antioxidant activity of hydrolysates. The crude WGPH produced in this way significantly inhibited angiotensin-I converting enzyme (ACE) in a concentration-dependent manner. It was next fractionated by reversed-phase semi-preparative High Performance Liquid Chromatography (HPLC) into 12 fractions that were examined for antioxidant and antihypertensive activities. Fractions with antioxidant and ACE-inhibitory activities were then submitted to further analysis by nano-LC-ESI-MS-MS. Among the various peptides identified, MDATALHYENQK (IC50 : 293.3±6.5µg/ml) and SGGSYADELVSTAK (IC50 : 265.5±8.3µg/ml) displayed antioxidant activity and VALTGDNGHSDHVVHF (IC50 : 189.3±4.05µg/ml), VDSLLTAAK (IC50 : 159.7±0.33µg/ml), MDATALHYENQK (IC50 : 303.6±2.47µg/ml), IGGIGTVPVGR (IC50 : 125.7±2.3µg/ml) and SGGSYADELVSTAK (IC50 : 128.2±1.17µg/ml) showed good ACE-inhibitory activity. PRACTICAL APPLICATIONS: Wheat milling industries produce massive amounts of wheat germ as by-product that can be converted into valuable compounds. The present research indicates that proteinase K is useful to hydrolyze wheat germ proteins in a search for bioactive peptides with antioxidant and ACE-inhibitory properties. The identified peptides can be regarded as functional food additives, or nutraceuticals to improve human health.