Trypanosoma cruzi: carboxylesterase activity in intact epimastigotes

Carboxylesterase activity corresponding to types A and B has been demonstrated in intact T. cruzi epimastigotes as shown by the hydrolysis of several esters of p-nitrophenol and the effect of suitable inhibitors. The in situ carboxylesterase activity was described by the Michaelis Menten kinetic approach. The apparent Vmax for the acetate and butyrate esters were 66.5 and 165.3 nmol hydrolysed per min and mg of protein respectively. An Arrhenius plot of the temperature dependent activity showed two sharp linear regions with a transition temperature of 31.6 degrees C. and energies of activation of 6.2 and 14.1 kcal/mol. The in situ carboxylesterase activity was inhibited 26% by paraoxon and 56% by N-ethylmaleimide, but not by p-chloromercuribenzoate.