Williams, R. A. M., Westrop, G. D. and Coombs, G. H. (2009) Two pathways for cysteine biosynthesis in Leishmania major. Biochemical Journal, 420(3), pp. 451-462. (doi: 10.1042/BJ20082441)
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Publisher's URL: http://dx.doi.org/10.1042/BJ20082441
Abstract
Genome mining and biochemical analyses have shown that <i>Leishmania major</i> possesses two pathways for cysteine synthesis--the de novo biosynthesis pathway comprising SAT (serine acetyltransferase) and CS (cysteine synthase) and the RTS (reverse trans-sulfuration) pathway comprising CBS (cystathionine beta-synthase) and CGL (cystathionine gamma-lyase). The LmjCS (<i>L. major</i> CS) is similar to the type A CSs of bacteria and catalyses the synthesis of cysteine using O-acetylserine and sulfide with K<sub>m</sub>s of 17.5 and 0.13 mM respectively. LmjCS can use sulfide provided by the action of MST (mercaptopyruvate sulfurtransferase) on 3-MP (3-mercaptopyruvate). LmjCS forms a bi-enzyme complex with <i>Leishmania</i> SAT (and Arabidopsis SAT), with residues Lys<sup>222</sup>, His<sup>226</sup> and Lys<sup>227</sup> of LmjCS being involved in the complex formation. LmjCBS (<i>L. major</i> CBS) catalyses the synthesis of cystathionine from homocysteine, but, unlike mammalian CBS, also has high cysteine synthase activity (but with the K<sub>m</sub> for sulfide being 10.7 mM). In contrast, LmjCS does not have CBS activity. CS was up-regulated when promastigotes were grown in medium with limited availability of sulfur amino acids. Exogenous methionine stimulated growth under these conditions and also the levels of intracellular cysteine, glutathione and trypanothione, whereas cysteine had no effect on growth or the intracellular cysteine levels, correlating with the low rate of transport of cysteine into the cell. These results suggest that cysteine is generated endogenously by promastigotes of <i>Leishmania</i>. The absence of CS from mammals and the clear differences between CBS of mammals and <i>Leishmania</i> suggest that each of the parasite enzymes could be a viable drug target.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Coombs, Professor Graham |
| Authors: | Williams, R. A. M., Westrop, G. D., and Coombs, G. H. |
| College/School: | College of Medical Veterinary and Life Sciences |
| Journal Name: | Biochemical Journal |
| Publisher: | Portland Press Ltd. |
| ISSN: | 0264-6021 |
| ISSN (Online): | 1470-8728 |
| Published Online: | 18 March 2009 |
| Related URLs: |
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