REGULATION OF A HIGH-AFFINITY DIAMINE TRANSPORT-SYSTEM IN TRYPANOSOMA-CRUZI EPIMASTIGOTES

Trypanosoma cruzi epimastigotes take up exogenous [H-3]putrescine and [3H]cadaverine by a rapid, high-affinity, transport system that exhibi ts saturable kinetics (putrescine K-m 2.0 mu M, V-max 3.3 nmol/min per 10(8) cells; cadaverine K-m 13.4 mu M, V-max 3.9 nmol/min per 10(8) c ells). Putrescine transport is temperature dependent and requires the presence of a membrane potential and thiol groups for activity. Its ac tivity is altered in response to extracellular putrescine levels and a s the cells proceed through th, growth cycle. This transporter shows h igh specificity for the diamines putrescine and cadaverine, but low sp ecificity for the polyamines spermidine and spermine. The existence of rapid diamine/polyamine transport systems whose activity can be adjus ted in response to the growth conditions is of particular importance, as they seem unable to synthesize their own putrescine [Hunter, Le Que sne and Fairlamb (1994) fur. J. Biochem. 226, 1019-1027].