Abstract

This is a summary of the recent work on some glycosidases of sand flies and their Leishmania parasites. Glycosidases catalyze the hydrolysis of complex sugar subunits of polysaccharides into simple sugars. Leishmania major parasites secrete chitinase and N-acetylglucosaminase, which enables them to survive in the gut of the sand fly and are important in facilitating their transmission by the phlebotomine sand fly Phlebotomus papatasi. These enzymes are found in a wide range of trypanosomatids and the gene locus is highly conserved. The sand flies feed on plants and the ingested tissues may contain cellulose particles that the sand flies are unable to digest. Cellulolytic enzymes are secreted by L. major promastigotes and this may help to break down cellulose in infected flies and sustain their growth. Starch is a main photosynthesis product that is stored in leaves. Starch grains have been found in the midguts of field caught sand flies and alpha-amylase, the specific enzyme for starch, has been found in the salivary glands and other organs of Lutzomyia longipalpis and P. papatasi. Alpha-amylase and alpha-glucosidase are expressed by L. major promastigotes and alpha-glucosidase is secreted by several trypanosomatid genera, but not by all those examined. Primers originally designed to amplify P. papatasi amylase DNA sequences, by polymerase chain reaction (PCR), also amplified DNA from all Old World Leishmania species, indicating that the gene is highly conserved between sand flies and these parasites.