PROPERTIES OF AN ARGINASE FROM THE COTYLEDONS OF PHASEOLUS-VULGARIS

In the cotyledons of Phaseolus vulgaris, the arginase activity reached a maximum at about 2-3 days of seed germination; thereafter, it began to decrease. The enzyme was partially purified and characterized. Can avanine was not a substrate and the K-m values for arginine were 45 +/ - 2 mM at the optimum pH of 9.6 and 93 +/- 5 mM at pH 7.5. Several met al ions activated the enzyme to a different degree (Mn2+ > Co2+ > Ni2 > Cd2+), but the K-m and K-i values were the same for all the metal a ctivated enzymes. Reactivation of fully inactivated enzyme by Mn2+ fol lowed hyperbolic kinetics with a K-d value of 0.47 +/- 0.05 mu M.