Different catalytic activities of hexokinase and phosphofructokinase in wild type and glucantime-resistant Leishmania promastigotes appears not causatively related to resistance

The changes which occur in the kinetics of two enzymes, hexokinase and phosphofructokinase, involved in glycolytic metabolism have been studied here, when resistance to Glucantime is induced in vitro into Leishmania tropica. The results show a significant reduction (62%) in the catalytic efficiency of hexokinase in the resistant line, with the reverse occurring when this line is grown in presence of the drug (increase of 57%), whereas the catalytic efficiency in phosphofructokinase increases significantly in the resistant line (169%), especially when it is grown in presence of Glucantime (538%). Presence of the drug during growth of the resistant parasite appears to induce the synthesis of these glycolytic enzymes, whilst the alteration of its kinetic parameters suggests a modification of the glycolytic flux through the action of Glucantime. However, the determination of enzyme activity in presence of the drug does not lead to important changes in this, suggesting that Glucantime has no direct effect on hexokinase and phosphofructokinase to justify its leishmanicidal effect.