PROTEINASE A-LIKE ENZYME FROM GERMINATED KIDNEY BEAN-SEEDS - ITS ACTION ON PHASEOLIN AND VICILIN

A cysteine proteinase that possibly participates in the degradation of phaseolin, the main storage protein of kidney bean (Phaseolus vulgari s L. cv. Moldavian) was isolated from germinating kidney bean seeds an d partially characterized. According to its properties it may be class ified as a member of a group of homologous cysteine proteinases A, als o present in germinating seeds of a number of other plants. The protei nase of this group hydrolyze storage proteins to short peptides. Simil arly, the kidney bean proteinase hydrolyzes vicilin, the reserve prote in of vetch (Vicia sativa), However, its action on phaseolin is limite d to the cleavage of subunits into two approximately equal parts and t o the splitting off a small number of short peptides. An explanation o f phaseolin resistance to the action of this proteinase is proposed on the basis of the differences of its structure from that of other homo logous 7S proteins.