Table 1

Kinetic parameters of pentamidine transporters in T. b. brucei and K _i values for purines and trypanocides (μM)

	PPT1^1-a	HAPT1^1-a	LAPT1^1-a	ASPT1^1-a	P2^1-b
Kinetic Parameters
K _m	0.029 ± 0.003	0.036 ± 0.006	56.2 ± 8.3	0.26 ± 0.03	0.43 ± 0.02^1-c ^1-f
V _max ^1-d	0.039 ± 0.008	0.0044 ± 0.0004	0.85 ± 0.15	0.068 ± 0.007	N/A
K _i values for inhibitors
Berenil	54 ± 16	63 ± 3	>250	2.5 ± 0.8	2.4 ± 0.5^1-f
Propamidine	3.7 ± 0.4	4.6 ± 0.7	>250	N.D.	1.9 ± 0.8
Stilbamidine	>250	56 ± 3	>250	N.D.	2.4 ± 0.3
Melarsen oxide	>100	>100	N.E., 100	0.63 ± 0.20	N.D.
Melarsoprol	N.D.	N.D.	N.D.	N.D.	0.54 ± 0.15^1-f
Adenosine	N.E., 1000	N.E., 1000	N.E., 1000	0.80 ± 0.12	0.92 ± 0.06^1-e ^1-f
Adenine	N.E., 1000	N.E., 1000	N.E., 1000	0.42 ± 0.04	0.45 ± 0.04^1-f

Bloodstream form or procyclic T. b. brucei was incubated with [³H]pentamidine as described under Experimental Procedures. Permeant concentrations were 12.5 nM (PPT1 and HAPT1), 1 μM (LAPT1), 12.5 or 25 nM (ASPT1), or 20 nM (P2). Results are expressed as the mean ± S.E. of at least three independent expts.

N.D., not determined; N.E., no effect at the indicated concentration.
↵1-a Using [³H]pentamidine.
↵1-b Using [³H]adenosine.
↵1-c K_i value for pentamidine.
↵1-d Expressed as pmol (10⁷cells)⁻¹ s⁻¹.
↵1-e K_m value.
↵1-f From De Koning and Jarvis (1999).