Glycolytic and chitinolytic activities of Phlebotomus papatasi (Diptera: Psychodidae) from diverse ecological habitats

Abstract

Abstract. The sand fly Phlebotomus papatasi Scopoli, 1786, the vector of Leishmania major Yakimoff et Schokhor, 1914, is found in desert areas where sugars are scarce but also in habitats that abound in sugar sources. The sand flies require sugar meals from plant sources for their energy requirements and to hydrolyze these complex sugars, they need a repertoire of glycosidases. We presumed that there are differences in the levels of glycosidase activities in flies from such habitats and also assumed that they may be instrumental in modulating the flies' susceptibility to L. major infections. Phlebotomus papatasi originating from diverse ecological habitats ranging from an oasis to desert sites were colonized. They were analyzed for weight changes and glycosidase activities before and after feeding on 1M sucrose solution. Oasis flies were smaller than desert flies but took larger sugar meals. Homogenates of these flies hydrolyzed 16 synthetic and 2 natural glycoside substrates to varying degrees. The arid-region flies tended to produce more glycosidase activity than those originating in sugar-rich environments, especially sucrase, α-and β-glucosidase, α-fucosidase, α-mannosidase, and α-and β-N-acetylgalactosaminidase. However, chitinolytic enzyme activities and particularly the β-N-acetylhexosaminidase activity of oasis flies were higher than other flies tested. In comparing the desert flies, there were also significant differences in glycolytic enzyme activities between the spring-line (flowering season) of flies and the autumn-line (end of dry season) flies. A range of saccharide inhibitors was tested to demonstrate the specificity of the enzymes.The energy requirements of both male and female sand flies are provided by staple sugar meals. Several different sources of sugar meals for both Phlebotomus and Lutzomyia species of sand flies have been described Killick-Kendrick 1987, Molyneux et al. 1991). Specifically, these meals are obtained directly by feeding on plant tissue or nectar (Schlein and

Standardization of a Continuous Assay for Glycosidases and Its Use for Screening Insect Gut Samples at Individual and Populational Levels

“…Methylumbelliferyl-based substrates have been used for a wide range of enzyme activities, but the dependence of the fluorescence on ionization of the group at high pHs has led to obligatory discontinuous assays for the majority of cases (Yang and Hamaguchi, 1980; Hoppe, 1983). Particularly, most insect glycosidases have optimal activities in acidic pHs (Gontijo et al, 1998; Terra and Ferreira, 2005; Jacobson et al, 2007; Cançado et al, 2008; Moraes et al, 2012; Tamaki et al, 2014; Moreira et al, 2015). In this way, the development of substrates with groups that fluoresce in acidic pHs would be greatly beneficial for the study of those enzymes.…”

“…Alternatively, colorimetric or fluorogenic groups from synthetic substrates as p -nitrophenol or methyl umbelliferyl derived glycosides are measured after release (Gontijo et al, 1998; Jacobson et al, 2007; Moraes et al, 2012; Vale et al, 2012; Moreira et al, 2015). In most cases, this results in obligatory discontinuous protocols.…”

“…GH activities have been extensively studied in different insect orders, including agricultural pests and disease vectors. They are responsible for the breaking down of molecules of plant and animal sources (Dillon and el-Kordy, 1997; Gontijo et al, 1998; Jacobson and Schlein, 2001; Terra and Ferreira, 2005; Jacobson et al, 2007; Mury et al, 2009; Fonseca et al, 2010; Ghadamyari et al, 2010; Moraes et al, 2012; Vale et al, 2012; Sellami and Jamoussi, 2016). …”

A Leishmania secretion system for the expression of major ampullate spidroin mimics

“…Another particularly abundant secreted protein is an invertase [28] that has been reported to contribute to the availability of metabolizable sugars from plant-derived polysaccharides present in the sandfly midgut [29]. It has been demonstrated that invertase secretion is directed by an N-terminal signal sequence (SS, [28]), that the signal sequence functions efficiently in secretion of recombinant invertase, and that the SS is absent from the mature protein [28].…”

A unique, highly conserved secretory invertase is differentially expressed by promastigote developmental forms of all species of the human pathogen, Leishmania

“…It is important to point out that all of these activities and developmental processes require an exogenous source of energy which the parasites must salvage/scavenge from the nutrients present within the insect vector midgut. To sustain themselves between their infectious blood feeds, female sand flies characteristically take plant juice meals including sucrose and other complex polysaccharides [7]. Following ingestion, such sugar meals are shunted and stored within the crop compartment of the insect’s gut.…”