THE PRESENCE OF COMPLEX-TYPE OLIGOSACCHARIDES AT THE C-TERMINAL DOMAIN GLYCOSYLATION SITE OF SOME MOLECULES OF CRUZIPAIN

Cruzipain is a lysosomal enzyme of the flagellate Trypanosoma cruzi. I t has three potential asparagine-glycosylation sites, two in the catal ytic domain and one in the C-terminal domain. The latter appeared to h ave both high mannose- and complex-type oligosaccharides, whereas the catalytic domain only had compounds of the former type. The partial su sceptibility of the complex-type compounds to endo-beta-N-acetylglucos aminidase H and their relative mannose and galactose content indicate that they had hybrid/monoantennary and biantennary structures. The sam e pattern of high mannose-type compounds was found at both domains, th us indicating that in cruzipain molecules having only high mannose-typ e compounds, all oligosaccharides were equally exposed to processing g lycosidases and glycosyltransferases. As heterogenity of the protein C -terminal domain has already been detected, it is suggested that this feature might elicit an increased accessibility to processing enzymes responsible for complex-type oligosaccharide formation in certain cruz ipain molecules or, alternatively, that a second glycosylation site wi th increased accessibility might be present in certain cruzipain molec ules. Furthermore, the presence of complex-type oligosaccharides stron gly suggests,that, as in mammalian cells, T. cruzi lysosomal enzymes t raverse the entire Golgi apparatus up to the trans-Golgi cisternae and the trans-Golgi network before reaching lysosomes.