Substrate specificity of the Trypanosoma cruzi trans-sialidase

Abstract

Trypanosoma cruzi trypomastigotes acquire sialic acid (SA) from host glycoconjugates by means of a plasma membrane-associated trans-sialidase (TS). Here we study the substrate specificity of TS, which differs from all known sialyltransferases in that it does not require cytidine monophosphate (CMP)-SA as donor. The T. cruzi TS reversibly transfers SA to saccharides with terminal beta-Gal (but not alpha-Gal) residues. Donors are saccharides with SA linked to terminal beta-Gal residues by (alpha 2-3), but not (alpha 2-6) bonds. The type of beta-linkage of the terminal Gal residue is of minor importance (beta 1-4 and beta 1-6 are slightly better than beta 1-3), whereas chain length and the structure of additional vicinal sugar residues are not relevant. SA on the surface of living trypomastigotes of T. cruzi is transferred back and forth between the parasite surface and acceptor molecules with terminal beta-Gal, either in solution or on the surface of neighbouring mammalian cells. Addition of fucose residue on or close to the terminal galactose impairs TS activity. As a consequence, the enzyme acts poorly on the E-selectin ligand sialyl-Lewisx and its precursor Lewisx, and in vitro adhesion of TS-treated neutrophils to L-cells expressing L-selectin is not affected. Modifications in the structure of the (alpha 2-3)-linked N-acetyl-neuraminic acid (Neu5Ac) (deoxy or methoxy) of the donor molecules do not impair transfer if the changes are at C9, whereas changes at C4, C7 and C8 impair the ability to donate the modified SA.(ABSTRACT TRUNCATED AT 250 WORDS)

Complete synthesis of 3′‐sialyl‐N‐acetyllactosamine by regioselective transglycosylation

“…The latter enzyme shows a better efficiency in transferring sialic acid to saccharides with terminal ~-galactose, rather than hydrolyzing it. This reaction results in the formation of the unique c~2-3 linkage between the terminal sialic acid and the galactose residue [14,27,28]. Few data have been reported on the use of trans-sialidase for synthetic goals [22,29,30].…”

Enzymatically Inactive trans-Sialidase from Trypanosoma cruzi Binds Sialyl and β-Galactopyranosyl Residues in a Sequential Ordered Mechanism

“…cruzi TS is an unusual sialidase with a predominant transglycosylase activity (21). The catalytic mechanism of trypanosomal sialidase (11) seems to be similar to viral sialidase (22) which is thought to hydrolyze the sialyl glycosidic bound through an oxocarbenium ion intermediate, with formation of trace amount of 2-deoxy-2,3-didehydro-N-acetylneuraminic (Neu5Ac2en) as a by-product.…”

Galactosyl-Lactose Sialylation Using Trypanosoma cruzi trans-Sialidase as the Biocatalyst and Bovine κ-Casein-Derived Glycomacropeptide as the Donor Substrate

“…It has strict regio-selectivity, however, for donor substrates possessing sialic acid bound via an (␣2-3) linkage to a terminal ␤-Gal (19,20); both N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) can be transferred (20,21). Various compounds possessing a terminal ␤-galactopyranose can be used as acceptor substrates, and due to its retaining mechanism, products formed by TcTS have a terminal Sia(␣2-3)Gal(␤1) unit (20).…”