The trans-sialidase from Trypanosoma cruzi efficiently transfers α-(2→3)-linked N-glycolylneuraminic acid to terminal β-galactosyl units

The trans-sialidase from Trypanosoma cruzi (TcTS), the agent of Chagas' disease, is a unique enzyme involved in mammalian host-cell invasion. Since T cruzi is unable to synthesize sialic acids de novo, TcTS catalyzes the transfer of alpha-(2 -> 3)-sialyl residues from the glycoconjugates of the host to terminal beta-galactopyranosyl units present on the surface of the parasite. TcTS also plays a key role in the immunomodulation of the infected host. Chronic Chagas' disease patients elicit TcTS-neutralizing antibodies that are able to inhibit the enzyme. N-Glycolylneuraminic acid has been detected in T cruzi, and the trans-sialidase was pointed out as the enzyme involved in its incorporation from host glycoconjugates. However, N-glycolylneuraminic acid alpha-(2 -> 3)-linked-containing oligosaccharides have not been analyzed as donors in the T cruzi trans-sialidase reaction. In this paper we studied the ability of TcTS to transfer N-glycolylneuraminic acid from Neu5Gc(alpha 2 -> 3)Gal(beta 1 -> 4)Glc beta OCH2CH2N3 (1) and Neu5Gc(alpha 2 -> 3) Gal(beta -> 3)GlcNAc beta OCH2CH2N3 (2) to lactitol, N-acetyllactosamine and lactose as acceptor substrates. Transfer from 1 was more efficient (50-65%) than from 2 (20-30%) for the three acceptors. The reactions were inhibited when the enzyme was preincubated with a neutralizing antibody. K-m values were calculated for 1 and 2 and compared with 3'-sialyllactose using lactitol as acceptor substrate. Analysis was performed by high-performance anion-exchange (HPAEC) chromatography. A competitive transfer reaction of compound 1 in the presence of 3'-sialyllactose and N-acetyllactosamine showed a better transfer of Neu5Gc than of Neu5Ac. (C) 2007 Elsevier Ltd. All rights reserved.