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

AGUSTI, R.; GIORGI, M.E.; LEDERKREMER, R.M.

Tilton, USA

Congreso; 2007 Gordon Conference on Carbohydrates; 2007

Gordon Research Conference

The trans-sialidase from Trypanosoma cruzi (TcTS), the agent of Chagasf disease, is a unique enzyme essential for the survival of the parasite in the mammalian or insect host.1 Since T. cruzi is unable to synthesize sialic acids de novo, TcTS catalyzes the transference of a(2-3) sialyl residues from host's glycoconjugates to terminal b-galactopyranosyl units present on the parasite surface molecules. On the other hand, TcTS plays a key role in the immunomodulation of the infected host. Animals that survive infection and chronic Chagasf disease patients elicit TcTS-neutralizing antibodies that are able to inhibit the enzymatic activity. TS-neutralizing antibodies are persistently found throughout the chronic phase of the infection and seem to circumscribe the enzyme activity in blood to the early steps of the infection both in patients and mice. N-Glycolylneuraminic acid (Neu5Gc) has been detected in Trypanosoma cruzi and the trans-sialidase was pointed out as the enzyme involved in its incorporation from host glycoconjugates. However, N-glycolylneuraminic acid a(2-3) linked-containing oligosaccharides have not been tested as donors in the Trypanosoma cruzi  trans-sialidase reaction. In the present work we studied the ability of TcTS to transfer Neu5Gc from Neu5Gc(a2-3)Gal(b1-4)GlcbOCH2CH2N3 (1) and Neu5Gc(a2-3)Gal(b1-3)GlcNAcbOCH2CH2N3 (2)2 to lactitol, N-acetyllactosamine and lactose as acceptor substrates. Transference from compound 1 was more efficient (transference values 50-65%) than from compound 2 (20-30%) for the three acceptor substrates. All the reactions were inhibited when the enzyme was preincubated with a neutralizing antibody. Km values were calculated for 1 and 2 and compared with 3f-sialyllactose using lactitol as acceptor substrate. Analysis was performed by high pH anion exchange chromatography (HPAEC-PAD). A competitive transfer reaction of compound 1 in the presence of 3f-sialyllactose and N-acetyllactosamine showed a better transference of Neu5Gc than of Neu5Ac. [1] Frasch, A.C. (2000) Parasitol. Today, 16, 282-286. 2 Blixt, O. and Paulson, J.C. (2003) Adv. Synth. Catal. 345, 687-690. The disaccharides were provided by the Consortium for Functional Glycomics.