ISSN:
1550-7408
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
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 Q10 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1550-7408.1999.tb05132.x
