Properties of a Mg2+ independent isocitrate lyase from gamma irradiated preclimacteric banana (Musa cavendishii)

Isocitrate lyase (Ee 4·1,3·1) was purified seventy fold from gamma irradiated banana pulp tissue acetone powder. It showed an optimum pH of 6·0, and the Km value for DL-isocitrate was 0·8 mM. Among the various metabolic inhibitors, oxaloacetate was found to be the most potent and its inhibition was competitive. The enzyme activity was not dependent on externally added Mg²⁺. The Mg²⁺ content of the purified enzyme was 10–12 ng/rng protein. A method for the detection of the two multiple forms of isocitrate lyase present in this preparation was developed using 2,4-dinitrophenylhydrazine as detecting agent for glyoxylate formed during the isocitrate lyase reaction.