Amylase isozymes in the mosquito, Culex tritaeniorhynchus

Phlebotomus papatasi and Leishmania major parasites express alpha-amylase and alpha-glucosidase

Alpha-amylase and alpha-glucosidase activities were found in homogenates of young, unfed male and female Phlebotomus papatasi and in gut and salivary gland preparations. A significant increase in both enzyme activities in females and of alpha-amylase in males was recorded for flies that had fed overnight on a plant (Capparis spinosa). After plant feeding, alpha-amylase activity was relatively lower in female salivary glands and higher in guts, while in the males the activity in the salivary glands had increased. Alpha-glucosidase activity increased in guts of both sexes and in the salivary glands of the females. In addition, alpha-amylase activity was found in preparations of Leishmania major and L. infantum promastigotes, but not in those of L. donovani or L. tropica. Alpha-glucosidase activity was present in promastigote preparations of L. major, L. infantum, L. donovani, L. braziliensis, Crithidia fasciculata and Herpetomonas muscarum. It was lacking in similar preparations of L. tropica, Sauroleishmania agamae or Leptomonas seymouri. The growth rate of L. major promastigotes in medium supplemented with starch or with glucose was similar and it was significantly higher than in glucose poor medium. In this study, we demonstrate that P. papatasi and L. major possess the enzymes for hydrolyzing starch grains that are included in the plant tissue-diet of the sand flies.

Salivary amylase activity of the phlebotomine sand fly, Lutzomyia longipalpis

Both male and female adult stages of the sand fly Lutzomyia longipalpis have detectable amylase activity in their salivary glands, as indicated by formation of p-nitrophenyl-alpha-D-maltoside from p-nitrophenyl-alpha-D-octoside and by hydrolysis of 4-nitrophenyl-alpha-D-maltoheptaoside-4,6,-O-ethylidene. No salivary alpha-glucosidase was detected. Amylase activity was also found in the crop and midgut of female flies, although in a smaller amount. Salivary amylase is significantly reduced from the salivary glands immediately after a blood meal, as is the case with salivary alpha-glucosidases in mosquitoes. Presence of salivary gland amylase in these sand flies, and absence of salivary alpha-glucosidase, indicates that in nature these insects may have a significant intake of carbohydrates in the form of starch, as suggested by their plant-feeding behavior, previously demonstrated by Schlein and Warburg (Schlein, Y., Warburg, A., 1986. Phytophagy and the feeding cycle of Phlebotomus papatasi (Diptera: Psychodidae) under experimental conditions. Journal of Medical Entomology 23, 11-15), and Alexander and Usma (Alexander, B., Usma, M.C., 1994. Potential sources of sugar for the phlebotomine sandfly Lutzomyia youngi (Diptera: Psychodidae) in a Columbia coffee plantation. Ann. Trop. Med. Parasitol. 88, 543-549).

The salivary glands of the vector mosquito, Aedes aegypti, express a novel member of the amylase gene family

Several cDNA clones with similarity to alpha-amylases have been characterized from a library made from adult female salivary gland RNA isolated from the vector mosquito, Aedes aegypti. The corresponding gene, designated Amylase I (Amy I), is expressed specifically in the proximal-lateral lobes of the adult female salivary gland, a pattern overlapping that of another gene, Mal I, involved in carbohydrate metabolism. The deduced amino acid sequence of Amy I indicates that this gene encodes a protein, approximate M(r) = 81,500, that appears to be a novel member of the amylase gene family. The mosquito protein contains a putative signal peptide for secretion and several consensus sites for asparagine-linked glycosylation. The Amy I protein shows significant similarity to invertebrate and vertebrate amylases including the conservation of four reactive and substrate binding sites. However, the amino-terminal region of the Amy-I protein is unique to the mosquito. Similarity with the Drosophila melanogaster protein is evident only after the first 260 amino acids in the mosquito sequence. The identification of this gene and its expression pattern adds to the observed relationship between spatial-specific gene expression in the female salivary glands and the specific feeding mode of the adult mosquito.