POLYMORPHIC FORMS OF UREASE FROM THE DEHUSKED SEEDS OF PIGEONPEA ( CAJANUS CAJAN L.)

摘要

Urease, purified from the dehusked seeds of pigeonpea (Cajanus cajan L.), was characterized for formation of polymorphic forms of the enzyme using polyacrylamide gel electrophoresis and activity staining techniques. The purified enzyme tended to form multimeric forms with three species of molecular mass of approximately 540, 600 and 700 kDa, respectively. Enzymatic activity was concentrated in the 540 kDa form and the polymorphic forms showed low (600 kDa) or no (700 kDa) catalytic activity. The formation of the polymorphic forms was a function of increasing salt concentration and presence of hydroxyl reagents. The multimeric forms had sulfhydryl bridges connecting them; addition of a reducing agent such as dithiothreitol (5 mM) resulted in formation of the basic unit of 540 kDa and loss of the higher molecular mass forms. Unlike urease from soybean or jack bean, no 240 kDa form was observed in any of the conditions studied.