When under stress, soil microorganisms such as some fungi or bacteria generally produce high concentrations of trehalose. In high concentrations, this disaccharide can selleck chemical protect proteins and cellular membranes from denaturation or injuries caused by extreme temperatures, desiccation and other factors (Elbein et al., 2003). Consequently, detritivorous larvae may be prepared to use this type of nutrient. In fact, L. longipalpis larvae promptly digest trehalose with one enzyme adhered to the midgut wall ( Fig. 10(b) where it is bound to the microvilli of the enterocytes.
The presence of a trehalase with an optimum pH of 6 can be inferred from the data presented in Fig. 9. The activity upon trehalose decreases considerably
at more alkaline pHs. In contrast, the α-glucolytic activity with maltose, sucrose and p-Np-α-d-glucopyranoside is nearly constant from pH 5.5 to 8 ( Fig. 9). Considering that in insects, trehalases are the only enzymes capable of hydrolyzing the disaccharide trehalose ( Terra and Ferreira, 1994), it is reasonable to infer the presence of an intestinal α-glucosidase and a trehalase in the midgut of the L. longipalpis larvae. Although selleck kinase inhibitor there is no definitive proof concerning this subject, fungi should be considered one of the main sources of nutrients for the phlebotomine larvae. This idea is in accordance with the results presented by Moraes et al. (2012) as well as in the present study. The N-acetyl-β-d-hexosaminidase inferred by the hydrolysis of the p-Np-N-acetyl-β-d-glucosaminide substrate is likely part of a chitinolytic apparatus used by the larvae to digest the cellular wall of the fungi. To be effective, this chitinolytic apparatus requires the presence of L-NAME HCl a soluble chitinase that should be produced preferentially in the anterior midgut. The role of the N-acetyl-β-d-hexosaminidase (such as that associated with the midgut
wall, see Table 1) should be to finalize the digestion of the chitin by acting on the oligosaccharides generated by this putative chitinase. Alternatively, this enzyme could be involved in glycoprotein digestion. Although we have not investigated the presence of the chitinase mentioned above, this enzyme seems to act in the midgut of L. longipalpis larvae, since the fluorogenic substrate 4-methylumbelliferyl-β-d-N′,N″,N‴N‴-triacetyl-chitotrioside was hydrolyzed by the midgut extract ( Moraes et al., 2012). In the present study we have explored the carbohydrate digestion by L. longipalpis larvae. Taken together, the data presented here show an overview of how polysaccharides as starch or glycogen are digested in the anterior midgut of the larvae and the products generated, hydrolyzed by membrane-bound enzymes in the posterior midgut. We expect in the next step of the study to investigate how the composition of the larval diet could modulate the production of different digestive carbohydrases.