Phosphofructokinase from the host fraction of chickpea nodules

Two phosphofructokinases (EC 2.7.1.11; PFK) have been isolated from the host fraction of nitrogen–fixing chickpea ( Cicer arietinum L.) root nodules that were formed with Rhizobium sp. (Cicer) CC1192. The predominant enzyme, which is suggested to be cytosolic, was isolated as a large aggregate of molecular mass near 2 000 kDa and was purified to a high degree. The less abundant enzyme, suggested to be of plastid origin, 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-phosphoglycerate and 3-phos-phoglycerate, and to a lesser extent by ADP, pyrophosphate, glucose-6-phosphate and 6-phosphogluconate. KCl and phosphate 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 fructose-6-phosphate.