title: 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)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.
authors.affiliation: Department of Biotechnology and Biochemistry, Centro de Investigacion y de Estudios Avanzados, Instituto Politécnico Nacional, Unidad Irapuato, Guanajuato, Mexico.
authors.forename: S
authors.initials: S
authors.lastname: Valdes-Rodriguez
authors.forename: M
authors.initials: M
authors.lastname: Segura-Nieto
authors.forename: A
authors.initials: A
authors.lastname: Chagolla-Lopez
authors.forename: A
authors.initials: A
authors.lastname: Verver y Vargas-Cortina
authors.forename: N
authors.initials: N
authors.lastname: Martinez-Gallardo
authors.forename: A
authors.initials: A
authors.lastname: Blanco-Labra
mesh_terms: D000595:Amino Acid Sequence; D019684:Magnoliopsida / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D012639:Seeds / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014361:Trypsin Inhibitors / Q000235:genetics* / Q000302:isolation & purification*
chemical_list: D014361:Trypsin Inhibitors