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 ± 6.5 µg/ml) and SGGSYADELVSTAK (IC50: 265.5 ± 8.3 µg/ml) displayed antioxidant activity and VALTGDNGHSDHVVHF (IC50: 189.3 ± 4.05 µg/ml), VDSLLTAAK (IC50: 159.7 ± 0.33 µg/ml), MDATALHYENQK (IC50: 303.6 ± 2.47 µg/ml), IGGIGTVPVGR (IC50: 125.7 ± 2.3 µg/ml) and SGGSYADELVSTAK (IC50: 128.2 ± 1.17 µg/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.

A Review on Health-Promoting, Biological, and Functional Aspects of Bioactive Peptides in Food Applications

“…Protein hydrolysates obtained from different sources show stronger antioxidant properties than their corresponding purified peptides [ 24 ]. There are many reports that describe antioxidant peptides from different food sources such as peanut protein [ 25 ], wheat germ [ 2 , 3 ], rice bran [ 26 ], sunflower [ 27 ], alfalfa leaf [ 28 ], corn gluten [ 29 ], frog skin [ 30 ], tuna liver [ 31 ], porcine liver [ 32 ], egg-yolk [ 33 ], milk and soymilk kefir [ 34 ], algae protein waste [ 35 ], and buckwheat protein [ 36 ]. The biological activity of these peptides, including antioxidant properties, is influenced by the processing conditions used in protein isolation, the protein type, the extent of hydrolysis, protease enzyme type, the structure of peptide, Mw of peptides, and peptide concentration, as well as proteolysis conditions such as substrate-to-enzyme ratio, pH, processing time, and temperature [ 29 , 37 ], as shown in Figure 2 .…”

“…Proteinase K is also useful to obtain bioactive peptides with ACE-inhibitory properties. In this regard, Karami et al [ 2 ] isolated the antihypertensive peptides IGGIGTVPVGR, SGGSYADELVSTAK, MDATALHYENQK, VDSLLTAAK, and VALTGDNGHSDHVVHF from wheat germ using proteinase K. They attributed this feature to the presence of basic residues such as R and K, or to aliphatic residues such as leucine (L), valine (V), alanine (A), or proline (P), or aromatics such as W, Y, or phenylalanine (F).…”

“…Particularly, a large range of bioactive peptides were identified from various food products. Bioactive peptides can be derived from animal and plant origins including soybean, cereals germ, potato, nuts, dairy products, egg, and meat proteins [ 1 , 2 , 3 , 4 ]. In the native sequences, these peptides do not show biological activity; however, they can be activated and exhibit biological activity by enzymatic, chemical, and microbial hydrolysis [ 5 ].…”

“…In the native sequences, these peptides do not show biological activity; however, they can be activated and exhibit biological activity by enzymatic, chemical, and microbial hydrolysis [ 5 ]. Enzymatic hydrolysis can be regarded as the most effective method to produce active peptides [ 1 , 2 ], which can be easily absorbed in intestinal tract and directly entered to the blood stream. This ensures their in vivo bioavailability and physiological functionality in the body [ 6 ].…”

Tryptophan targeted pulsed electric field treatment for enhanced immune activity in pine nut peptides

“…Most bioactive peptides came from food ingredients. For example, through enzymatic hydrolysis of pollen protein (Maqsoudlou et al, 2019), wheat germ protein (Karami, Peighambardoust, Hesari, Akbari‐Adergani, & Andreu, 2019), lupine protein (Lammi, Zanoni, Arnoldi, & Aiello, 2018), and wild hazelnut protein (Fang et al, 2019), bioactive peptides with high angiotensin converting enzyme inhibitory activity, hypotensive activity, cholesterol lowering activity, and antioxidant activity could be obtained, respectively. The purified peptide YLVR from hazelnut had a strong inhibitory effect on angiotensin‐I‐converting enzyme (Liu, Fang, Min, Liu, & Li, 2018).…”