Abstract
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 α-glucosidases, are the main enzymes involved in the digestion of sugars. In this context, we studied the modulation of α-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 MUαGlu and sucrose, with highest activities in the midgut and crop. Activity was 1,000 times higher on sucrose than on MUαGlu. Basal activities were observed in non-fed insects; blood feeding induced activity in the midgut contents, and sugar feeding modulated activity in midgut tissues. α-glucosidase activity changed after female exposure to different sugar concentrations or moieties. α-glucosidases from different tissues showed different biochemical properties, with an optimum pH around 7.0–8.0 and KM between 0.37 and 4.7 mM, when MUαGlu was used as substrate. Using sucrose as substrate, the optimum pH was around 6.0, and KM ranges between 11 and 800 mM. Enzymes from the crop and midgut tissues showed inhibition in high substrate concentrations (sucrose), with KI ranging from 39 to 400 mM, which explains the high KM values found. Chromatographic profiles confirmed that different α-glucosidases are been produced in L. longipalpis in different physiological contexts, with the distinction of at least four α-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.
Highlights
There are approximately 900 species of phlebotomines and about 98 of these species are considered of medical importance, being vectors of diseases such as visceral and cutaneous leishmaniasis, bartonellosis, besides transmitting other trypanosomatids and arboviruses (Sherlock, 2003; Bates et al, 2015; Oryan and Akbari, 2016; WHO, 2017).Leishmaniasis are caused by more than 20 species of Leishmania (Akhoundi et al, 2016)
The results show that the activity is much higher on sucrose than on MUαGlu, showing the preference of these enzymes for the natural substrate
We demonstrate the presence of α-glucosidase activity in all tissues of L. longipalpis unfed females, using two different substrates (Figure 1)
Summary
There are approximately 900 species of phlebotomines and about 98 of these species are considered of medical importance, being vectors of diseases such as visceral and cutaneous leishmaniasis, bartonellosis, besides transmitting other trypanosomatids and arboviruses (Sherlock, 2003; Bates et al, 2015; Oryan and Akbari, 2016; WHO, 2017). The energy obtained by the hydrolysis of these sugars is a crucial factor for insect development and maintenance of a sufficient lifetime for infection with Leishmania and its subsequent transmission This enzyme may participate in the final digestion of blood glycoproteins and glycolipids. The detailed description of the specificity, function, and structure of the α-glucosidases of L. longipalpis may provide the basis for the development of new strategies to control these insects and block the transmission of the disease, due to the importance of this enzyme in the digestion process in these insects and in the relationship between host and parasite. At least four different α-glucosidases with distinct biochemical properties were found, as constitutive or induced, in different feeding conditions They appear to be involved in different metabolic processes, like digestion of plant sugars, digestion of blood glycoproteins or glycolipids, and mobilization of energetic storages during starvation
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