The developmentally regulated trans-sialidase from Trypanosoma brucei sialylates the procyclic acidic repetitive protein.
A developmentally regulated trans-sialidase activity is present on the surface of procyclic Trypanosoma brucei. Bloodstream stages display no trans-sialidase activity. T. brucei trans-sialidase is capable of transferring sialic acids from a variety of glycoconjugates into new glycosidic linkages without requirement for CMP-Neu5Ac. The enzyme is linked to the plasma-membrane via a GPI-PLC-resistant GPI-anchor. The comparison of enzymic and structural features of sialidase and trans-sialidase suggests that the two activities may be catalyzed by the same protein, since highly enriched sialidase fractions display trans-sialidase activity. 2-Deoxy-2,3-didehydro-N-acetylneuraminic acid is only a poor inhibitor for the two enzymic activities. Sialic acids are transferred to alpha (2-3)-positions of terminal beta-galactose residues of oligosaccharides and glycoconjugates at various rates. Neu5Ac-alpha(2-3)-lactose is the best trans-sialylation donor tested. Lewis is a poor sialic acid acceptor. T. brucei trans-sialidase utilizes serum glycoconjugates, human and bovine erythrocytes as sialic acid donors, and resialylates sialidase-treated erythrocytes. The enzyme transfers sialic acids from the GPI-anchor of procyclic acidic repetitive protein (PARP) onto lactose and vice versa. Also structures within a variant surface glycoprotein (sVSG MITat. 1.7.) can be trans-sialylated.
Engstler
M
M
Biochemisches Institut, Christian-Albrechts-Universität, Kiel, Germany.
Reuter
G
G
Schauer
R
R
D000818:Animals; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism; D012794:Sialic Acids / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000254:growth & development; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000378:metabolism*
D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012794:Sialic Acids; D014643:Variant Surface Glycoproteins, Trypanosoma; C053277:procyclic acidic repetitive protein, Trypanosoma; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid