PHOSPHOFRUCTOKINASE FROM THE HOST FRACTION OF CHICKPEA NODULES

Two phosphofructokinases (EC 2.7.1.11; PFK) have been isolated from th e host fraction of nitrogen-fixing chickpea (Cicer arietinum L.) root nodules that were formed with Rhizobium sp. (Cicer) CC1192. The predom inant enzyme, which is suggested to be cytosolic, was isolated as a la rge aggregate of molecular mass near 2 000 kDa and was purified to a h igh degree. The less abundant enzyme, suggested to be of plastid origi n, had a native molecular mass of 186 kDa. Both forms of PFK displayed typical hyperbolic kinetics with MgATP and fructose-6-phosphate. The major form of PFK was strongly inhibited by phosphoenolpyruvate, 2-pho sphoglycerate and 3-phosphoglycerate, and to a lesser extent by ADP, p yrophosphate, glucose-6-phosphate and 6-phosphogluconate. KCl and phos phate were activators and relieved the effect of inhibitors. The major PFK was disaggregated in the presence of ATP into a species which had a molecular mass of approximately 550 kDa and a lower affinity for fr uctose-6-phosphate.