Characterization of LdLIP3 Enzyme Activity from Leishmania donovani
Lipases catalyze the hydrolysis of fats to form glycerol and fatty acids. Secreted lipases have been implicated as virulence factors in some pathogens. Previously a gene encoding a secretory lipase from the human protozoan pathogen Leishmania donovani was identified and characterized however, experimental evidence to support the biological role of secreted lipases in Leishmania sp. remains to be elucidated. The goal of this project was to express the secretory lipase gene, LdLIP3, from L. donovani and characterize its lipolytic activity. Culture supernatants of L. donovani over-expressing the secretory LdLIP3 enzyme were used to characterize lipolytic activity at several different pHs and temperatures that are biologically relevant in the life cycle of the parasite. At 26°C the optimal lipolytic activity was determined to be pH5.0 with palmitate as the substrate. Similarly, at 37°C the optimal activity was at pH 6.5 with palmitate, and at 42°C, pH 6.0 using stearate as substrate. These results indicate that LdLIP3 has lypolytic activity that could be significant throughout the parasite life cycle. Characterization of the optimal lipolytic activity for the LdLIP3 enzyme should allow further analysis of the physical and biochemical properties of the secreted lipase and to define its possible role in the life cycle of Leishmania sp.