Characterization of α-Glucosidases From Lutzomyia longipalpis Reveals Independent Hydrolysis Systems for Plant or Blood Sugars

Lutzomyia longipalpis is the main vector of Leishmania infantum and exploits different food sources during development. Adults have a diet rich in sugars, and females also feed on blood. The sugar diet is essential for maintaining longevity, infection, and Leishmaniasis transmission. Carbohydrases, including alpha-glucosidases, are the main enzymes involved in the digestion of sugars. In this context, we studied the modulation of alpha-glucosidase activities in different feeding conditions and compartments of Lutzomyia longipalpis females, in order to characterize in detail their roles in the physiology of this insect. All tissues showed activity against MU alpha Glu and sucrose, with highest activities in the midgut and crop. Activity was 1,000 times higher on sucrose than on MU alpha Glu. Basal activities were observed in non-fed insects; blood feeding induced activity in the midgut contents, and sugar feeding modulated activity in midgut tissues. alpha-glucosidase activity changed after female exposure to different sugar concentrations or moieties. alpha-glucosidases from different tissues showed different biochemical properties, with an optimum pH around 7.0-8.0 and K-M between 0.37 and 4.7 mM, when MU alpha Glu was used as substrate. Using sucrose as substrate, the optimum pH was around 6.0, and K-M ranges between 11 and 800 mM. Enzymes from the crop and midgut tissues showed inhibition in high substrate concentrations (sucrose), with K-I ranging from 39 to 400 mM, which explains the high K-M values found. Chromatographic profiles confirmed that different alpha-glucosidases are been produced in L. longipalpis in different physiological contexts, with the distinction of at least four alpha-glucosidases. The results suggest that some of these enzymes are involved in different metabolic processes, like digestion of plant sugars, digestion of blood glycoproteins or glycolipids, and mobilization of energetic storages during starvation.