PLANT PHYSIOLOGY , Vol 103, Issue 4 1407-1412, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Purification, Characterization, and Complete Amino Acid Sequence of a Trypsin Inhibitor from Amaranth (Amaranthus hypochondriacus) Seeds
S. Valdes-Rodriguez, M. Segura-Nieto, A. Chagolla-Lopez, AVy. Vargas-Cortina, N. Martinez-Gallardo and A. Blanco-Labra
Department of Biotechnology and Biochemistry (S.V.-R., A.C.-L., N.M.-G., A.B.-L.) and Department of Genetic Engineering (M.S.-N., A.V.V.-C.), Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Unidad Irapuato, Apdo. Postal 629, C.P. 36500, Irapuato, Guanajuato, Mexico
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 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.
