Characterization of protein-linked oligosaccharides in trypanosomatid flagellates

Abstract

Protein-linked, endo- β- N-acetylglucosaminidase H-sensitive oligosaccharides were isolated from several trypanosomatids incubated with [U- 14C]glucose. Structural analysis of the compounds revealed that Man 9GlcNAc 2 was the oligosaccharide transferred from dolichol-P-P derivatives to proteins in Trypanosoma dionisii, Trypanosoma conorhini, Leptomonas samueli and Herpetomonas samuelpessoai and Man 6GlcNAc 2 in Blastocrithidia culicis and Leishmania adleri. In all cases, transiently glucosylated compounds were detected: Glc 1Man 7–9GlcNAc 2 in T. dionisii, T. conorhini, L. samueli; Glc 1Man 9GlcNAc 2 in H. samuelpessoai, Glc 1Man 6GlcNAc 2 in B. culicis and Glc 1Man 6GlcNAc 2 and Glc 1Man 5GlcNAc 2 in L. adleri. The mechanism of protein glycosylation in T. dionisii and T. conorhini appeared to be similar to that described before for Trypanosoma cruzi epimastigotes, although some differences were found between the structures of the main isomers of Man 7GlcNAc 2 and Man 8GlcNAc 2 present in T. conorhini and T. cruzi. Differences between the mechanisms of glycosylation occurring in Leishmania mexicana and L. adleri were also found: Man 6GlcNAc 2 in the latter microorganism was demannosylated to Man 5GlcNAc 2, a step not detected in the former parasite. A novel substituent in N-linked high mannose-type oligosaccharides was found in L. samueli and H. samuelpessoai: galactose in the furanose configuration. In the latter trypanosomatid, Man 9GlcNAc 2 was demannosylated only to Man 8GlcNAc 2, whereas in all other parasites in which the same oligosaccharide was transferred to proteins, Man 5–7GlcNAc 2 were also detected.