Trypanosomatids have been shown to possess an exclusive and finely regulated biosynthetic pathway for de novo synthesis of fatty acids (FAs) and particularly of polyunsaturated fatty acids (PUFAs). The key enzymes for the process of unsaturation are known as desaturases. In this work, we explored the biocatalytic activity of the putative Delta6-desaturase (Tb11.v5.0580) in the native organism T. brucei. Utilising fatty acid analysis via GC-MS, we were able to elucidate via genetic manipulation of the level of expression of Delta6-desaturases in both procyclic (PCF) and bloodstream (BSF) forms of T. brucei and via supplementation of the media with various levels of FA sources, that docosahexaenoic acid (22:6) and/or docosapentaenoic acid (22:5), and arachidonic acid (20:4) and/or docosatetraenoic acid (22:4) are the products and the substrates respectively of this Delta6-desaturases. Interestingly, we were able to observe via lipidomic analysis with ESI-MS/MS, an increase in inositol-phosphoryl ceramide (IPC) in response to the overexpression of Delta6-desaturases in low-fat media, both in PCF and rather surprisingly in BSF. The formation of IPC is normally only observed in the stumpy and procyclic forms of T. brucei. Therefore, the expression levels of Delta6-desaturases, which varies between BSF and PCF, might be involved in the cascade(s) of metabolic events that cause these remodelling of the lipid pools and ultimately morphological changes, which are key to the transition between these life-cycle stages.

Exploring the activity and the essentiality of the putative Delta6-desaturase in the procyclic and bloodstream forms of Trypanosoma brucei