HYSTERESIS OF CYTOSOLIC NADP-MALIC ENZYME II FROM TRYPANOSOMA-CRUZI

NADP-malic enzyme II, one of two isoenzymes of NADP-malic enzyme (EC 1 .1.1.40) in Trypanosoma cruzi epimastigotes, presents hysteretic behav ior that results in a kinetic lag in the reaction progress curve. The lag is affected by the malate, aspartate and oxalacetate concentration s in the assay mixture. This dependence suggests that hysteresis is du e to an association-dissociation process influenced by the binding of these ligands to the enzyme. The enzyme was separated from NADP-malic enzyme I and purified 43-fold from a cell homogenate by a procedure in volving column chromatography on DEAE-Sephacel and Cibacron-blue Sepha rose. The molecular mass of the highly purified enzyme was determined as 126 kDa.