Valdes-Rodriguez S, Segura-Nieto M, Chagolla-Lopez A, Verver y Vargas-Cortina A, Martinez-Gallardo N, Blanco-Labra A. Purification, characterization, and complete amino acid sequence of a trypsin inhibitor from amaranth (Amaranthus hypochondriacus) seeds.
Plant Physiol 1993;
103:1407-1412. [PMID:
8290633 PMCID:
PMC159133 DOI:
10.1104/pp.103.4.1407]
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Abstract
A protein proteinase inhibitor was purified from a seed extract of amaranth (Amaranthus hypochondriacus) by precipitation with (NH4)2SO4, 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 Prostephanus truncatus. This inhibitor belongs to the potato-I 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 Cucurbita maxima. The position of the lysine-aspartic 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.
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