Biosynthesis of polyunsaturated fatty acids in trypanosomatids

UTTARO, ANTONIO D.

Caxambu

Congreso; XXI Meeting of the Brazilian Society of Parasitology and XXXII Meeting on Basic Research in Chagas Disease; 2005

The completion of the three kinetoplastid genome projects allowed us to identify genes that codify for enzymes involved in desaturation and elongation of fatty acids. We have functionally characterized all the enzymes of the polyunsaturated fatty acid (PUFA) biosynthetic pathway from Trypanosoma brucei and Leishmania major. These results can be extended to Trypanosoma cruzi, by phylogenetic analysis and primary structural studies, indicating the presence of a pathway similar to that from T. brucei. Functional characterization has been done by the heterologous expression of desaturase and elongase genes in Saccharomyces cerevisiae and the analysis of the yeast lipid profiles by gas chromatography-mass spectrometry. Our results indicate that L. major is able to de novo synthesize 22:5 n-6 and 22:6 n-3 PUFAs by the consecutive action of a stearoyl CoA D9 desaturase, oleate (D12) desaturase, w3 desaturase, D6 desaturase, D6 elongase, D5 desaturase, D5 elongase and a D4 desaturase. It represents the first pathway completely described for PUFA biosynthesis in a protozoon. On the other hand, T. brucei and T. cruzi are able to synthesize 18: 2 D9,12 by the action of stearoyl CoA D9 desaturase and oleate desaturase. No other enzymes for PUFA biosynthesis appear to be present in trypanosomes with the exception of D5 elongase and D4 desaturase, indicating that the production of C22 PUFAs, from exogenous substrate(s), is essential in these organisms. C18 PUFAs represent up to 80% of total fatty acids in trypanosomatids. They are probably essential for the parasites in order to adapt themselves to the dramatic changes in temperature and morphology experienced during their complex life cycles. Inhibition of desaturase activities by RNA interference in T. brucei or by using fatty acid analogues, allowed us to validate these enzymes as putative chemotherapeutic targets. D9 desaturase, oleate (D12) desaturase, w3 desaturase, D6 desaturase, D6 elongase, D5 desaturase, D5 elongase and a D4 desaturase. It represents the first pathway completely described for PUFA biosynthesis in a protozoon. On the other hand, T. brucei and T. cruzi are able to synthesize 18: 2 D9,12 by the action of stearoyl CoA D9 desaturase and oleate desaturase. No other enzymes for PUFA biosynthesis appear to be present in trypanosomes with the exception of D5 elongase and D4 desaturase, indicating that the production of C22 PUFAs, from exogenous substrate(s), is essential in these organisms. C18 PUFAs represent up to 80% of total fatty acids in trypanosomatids. They are probably essential for the parasites in order to adapt themselves to the dramatic changes in temperature and morphology experienced during their complex life cycles. Inhibition of desaturase activities by RNA interference in T. brucei or by using fatty acid analogues, allowed us to validate these enzymes as putative chemotherapeutic targets.