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L‐Arginine Uptake and L‐Phosphoarginine Synthesis In Trypanosoma Cruzi
Author(s) -
PEREIRA CLAUDIO A.,
ALONSO GUILLERMO D.,
PAVETO M. CRISTINA,
FLAWIÁ MIRTHA M.,
TORRES HÉCTOR N.
Publication year - 1999
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.1999.tb05132.x
Subject(s) - arginine , arginine kinase , trypanosoma cruzi , biology , ornithine , biochemistry , amino acid , sodium , citrulline , mole , microbiology and biotechnology , incubation , chemistry , parasite hosting , organic chemistry , world wide web , computer science
A very specific L‐arginine transporter showing high affinity has been characterized in Trypanosoma cruzi epimastigotes. Uptake was found to be dependent on L‐arginine concentration and it was saturable. Values for maximum velocity and Km ranged between 48.1‐57.5 pmol·min ‐1 per 3 times 10 ‐ cells and between 4.2‐5.5 μM, respectively. the calculated activation energy and Q 10 were 31.1 KJ·mol ‐1 , and 1.7, respectively. Uptake velocity significantly increased when cells were preincubated in the absence of L‐arginine, Cells retained the labeled amino acid independently of the presence or absence of exogenous L‐arginine. the specificity of L‐arginine uptake was demonstrated by competition assays in the presence of 80‐fold molar excess of natural amino acids and several L‐arginine derivatives. the highest levels of inhibition were caused by L‐homoarginine, D‐arginine, L‐canavanine, L‐ornithine, and L‐citrulline. L‐arginine uptake by T. cruzi epimastigotes was not affected by the presence of potassium or sodium ions in the incubation mixture or by pH changes in the range between 5.5‐8.5. the major product of L‐arginine uptake was characterized as phosphoarginine. Moreover, arginine kinase activity was detected in soluble extracts from T. cruzi epimastigotes.