Purification, Characterization, and Complete Amino Acid Sequence of a Trypsin Inhibitor from Amaranth (Amaranthus hypochondriacus) Seeds

Abstract

A protein proteinase inhibitor was purified from a seed extract of amaranth (Amaranthus hypochondriacus) by precipitation with (NH4)2S04, gel-filtration chromatography, ion-exchange chromatography, and reverse-phase high-performance liquid chromatography. It is a 69-amino acid protein with a high content of valine, arginine, and glutamic acid, but lacking in methionine. The inhibitor has a relative molecular weight of 7400 and an isoelectric point of 7.5. It is a serine proteinase inhibitor that recognizes chymotrypsin, trypsin, and trypsin-like proteinase activities extracted from larvae of the insect Prosfephanus fruncafus. This inhibitor belongs to the potato-l inhibitor family, showing the closest homology (59.5%) with the Lycopersicum peruvianum trypsin inhibitor, and (51%) with the proteinase inhibitor 5 extracted from the seeds of Cucurbifa maxima. The position of the lysineaspartic acid residues present in the active site of the amaranth inhibitor are found in almost the same relative position as in the inhibitor from C. maxima.

Effects of natural protease inhibitors on high protease activity flours

“…Other plants such as seeds of amaranth (Rodriguez et al, 1993), chickpea (Harsulkar et al, 1997), sunflower (Konarev et al, 2000), maize (Ellatif, 2014), and seeds or leaves of peppers (Montes et al, 2014) have been most extensively studied plants for their proteinase inhibitor contents. The most known proteinase inhibitors are active against digestive proteinases found in animals and microorganisms.…”

Functional and Rheological Properties of Amaranth Albumins Extracted From Two Mexican Varieties

“…Albumins are defined by their solubility in water or in low ionic strength solutions; in this fraction it was found to be a group of 2S polypeptides, called 2MRPs, with 16-18% methionine content, and a molecular weight of 18 kDa [6]. In spite of the presence of antinutritional factors including phenolic substances, trypsin inhibitor and cytoaglutinins, the amaranth grain continues being one of the grains with the most potential food and feed resources [10,11]. In fact, currently, trypsin inhibitors are taking great attention as nutraceutical compounds, which add the advantageous properties of the amaranth grain.…”

Effects of heat and pH treatments and in vitro digestion on the biological activity of protein hydrolysates of Amaranthus hypochondriacus L. grain

“…Because T and C are serin proteases, the activity of the residual peptide, called amaranth trypsin/subtilisin inhibitor (ATSI), present in protein hydrolysates of amaranth grain, was also assessed. ATSI inhibitory activity was evaluated following the protocol by Valdes-Rodriguez et al (1993). Alb1H103 with a % HD = 42.1 ± 0.4 had a % Inh ATSI = 35.4 ± 0.6, whereas GloH88 with a % HD = 16.3 ± 1.7 displayed a higher inhibitory activity of serin proteases (%Inh ATSI = 46.4 ± 0.8).…”