Abstract
The purine base transport systems of wild-type and mycophenolic acid-resistant (MPAR) Tritrichomonas foetus have been characterized. Wild-type T. foetus has two carriers, one for hypoxanthine (Km = 0.7 ± 0.3 mM, Vm = 80 ± 20 pmol μl−1min−1) and guanine (Km = 0.09 ± 0.02 mM, Vm = 17 ± 3 pmol μl−1min−1), and a second for xanthine (Km = 0.6 ± 0.2 mM, Vm = 25 ± 5 pmol μl−1min−1). Adenine transport was not saturable (k = 0.16 ± 0.01 min−1) and therefore appears to enter the parasite by passive diffusion through the membrane. T. foetus MPAR has lost the hypoxanthine/guanine transporter. Xanthine and adenine transport are similar in wild-type and MPART. foetus. No purine nucleoside transporter could be identified.