Composition of the peritrophic matrix of the tsetse fly, Glossina morsitans morsitans

The three-layered peritrophic matrix of Glossina morsitans morsitans is shown, by histochemistry, to be formed of a mixture of glycosaminoglycans, glycoproteins and chitin. In all three layers the glycosaminoglycans contain GlcNAc-hexuronic and Gal-GlcNAc moieties, together with chitin. Glycosaminoglycans in layer 3 are sulphated and sulphated sites have a mean interspace distance of 53 nm - similar to the spacing of fixed charge sites in glomerular basement membrane suggesting a role for these sites in the filtration properties of the peritrophic matrix. O-linked oligosaccharides are present in all three layers. Layer 1 contains the widest variety of glycoprotein oligosaccharide constructs GlcNac and alpha linked GalNAc possibly as GalNAc alpha 1,3GalNAc, the latter apparently distal to Gal beta 1-4GalNAc. Lectin binding suggests that layer 2 contains GalNAc alpha 1,3Gal beta 1,3GlcNAc and that layer 3 contains GalNAc and Gal beta 1,4GlcNAc. The evidence for N-Linked oligosaccharides is more equivocal. Two dimensional electrophoresis showed that the peritrophic matrix contains a range of proteins, most of which require relatively harsh treatment for their solubilization.