| Abstract: | An acidic glycoconjugate containing mannose, galactose and phosphate in approximately equimolar amounts was extracted from Leishmania donovani promastigotes and partially characterized. The glycoconjugate could be metabolically labeled with either 3H]mannose or 3H]galactose and was extractable from a delipidated residue fraction with water/ethanol/diethyl ether/pyridine/concentrated NH4OH (15:15:5:1:0.017) at 25 degrees C. The radioactively labeled glycoconjugate was found to possess the following characteristics: 1) comprised 45-60% of the total 3H]mannose label incorporated into macromolecules; 2) was soluble in alkaline solvents and 0.5% Triton X-100; 3) migrated as a broad band upon electrophoresis on sodium dodecyl sulfate-polyacrylamide gels with an approximate molecular weight of 15,000-30,000; 4) bound to DE52 cellulose and was eluted with a salt gradient of 0-0.1 M NaCl; 5) was insensitive to Pronase, hyaluronidase, chondroitinase, endo-beta-N-acetylglucosaminidase H, and endo-beta-galactosidase; and 6) possessed hydrophobic properties. An unusual feature of the glycoconjugate was its lability to mild acid hydrolysis (0.02 N HCl, 15 min, 60 degrees C). As determined by alkaline phosphatase and glycosidase digestion and paper chromatographic analysis, the major fragment generated by mild acid hydrolysis was found to be a phosphorylated galactosyl-beta-mannose disaccharide. All of these characteristics suggest that the glycoconjugate may be a polysaccharide and, possibly, may be important in parasite-host cell interactions. |
