Biochemical characterization of the glutamate transport in Trypanosoma cruzi

被引:26
作者
Silber, AM
Rojas, RLG
Urias, U
Colli, W
Alves, MJM
机构
[1] Univ Sao Paulo, Inst Biociencias, Dept Fisiol, BR-05508900 Sao Paulo, Brazil
[2] Univ Sao Paulo, Inst Quim, Dept Bioquim, BR-01498 Sao Paulo, Brazil
基金
巴西圣保罗研究基金会;
关键词
Trypanosoma cruzi; Chagas' disease; amino acid metabolism; metabolite transporter; glutamate;
D O I
10.1016/j.ijpara.2005.10.006
中图分类号
R38 [医学寄生虫学]; Q [生物科学];
学科分类号
07 ; 0710 ; 09 ; 100103 ;
摘要
The role of amino acids in trypanosomatids goes beyond protein synthesis, involving processes such as differentiation, osmoregulation and energy metabolism. The availability of the amino acids involved in those functions depends, among other things, oil their transport into the cell. Here we characterize a glutamate transporter from the human protozoan parasite Trypanosoma cruzi. Kinetic data show a single saturable system with a Km of 0.30 mM and a maximum velocity of 98.34 pmoles min(-1) per 2x10(7) cells for epimastigotes and 20 pmoles min(-1) per 2x10(7) cells for trypomastigotes. Transport was not affected by parasite nutrient starvation for up to 3 h. Aspartate, alanine, glutamine, asparagine, methionine, oxaloacetate and alpha-ketoglularate competed with the substrate in 10-fold excess concentrations. Glutamate uptake was strongly dependent on pH, but not oil Na+ or K+ concentrations in the extracellular medium. These data were consistent with the sensitivity of the system to the H+ ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone, suggesting that transport is driven by H+ concentration gradient across the cytoplasmic membrane. The glutamate transport increased linearly with temperature in a range from 15 to 40 degrees C, allowing the calculation of an activation energy of 52.38 kJ/mol. (C) 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.
引用
收藏
页码:157 / 163
页数:7
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