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

AGUSTI R; GIORGI M. E; LEDERKREMER RM

New Hampshire

Conferencia; Gordon Conference on Carbohydrates; 2007

Gordon Conference on Carbohydrates

The trans-sialidase from Trypanosoma cruzi (TcTS), the agent of Chagas?disease, is a unique enzyme essential for the survival of the parasite in the mammalianor insect host.1 Since T. cruzi is unable to synthesize sialic acids de novo, TcTScatalyzes the transference of α(2→3) sialyl residues from host?s glycoconjugates toterminal β-galactopyranosyl units present on the parasite surface molecules.On the other hand, TcTS plays a key role in the immunomodulation of theinfected host. Animals that survive infection and chronic Chagas? disease patients elicitTcTS-neutralizing antibodies that are able to inhibit the enzymatic activity. TSneutralizingantibodies are persistently found throughout the chronic phase of theinfection and seem to circumscribe the enzyme activity in blood to the early steps of theinfection both in patients and mice.N-Glycolylneuraminic acid (Neu5Gc) has been detected in Trypanosoma cruziand the trans-sialidase was pointed out as the enzyme involved in its incorporationfrom host glycoconjugates. However, N-glycolylneuraminic acid α(2→3) linkedcontainingoligosaccharides have not been tested as donors in the Trypanosoma cruzitrans-sialidase reaction.In the present work we studied the ability of TcTS to transfer Neu5Gc fromNeu5Gc(α2→3)Gal(β1→4)GlcβOCH2CH2N3 (1) andNeu5Gc(α2→3)Gal(β1→3)GlcNAcβOCH2CH2N3 (2)2 to lactitol, N-acetyllactosamineand lactose as acceptor substrates. Transference from compound 1 was more efficient(transference values 50-65%) than from compound 2 (20-30%) for the three acceptorsubstrates. All the reactions were inhibited when the enzyme was preincubated with aneutralizing antibody. Km values were calculated for 1 and 2 and compared with 3?-sialyllactose using lactitol as acceptor substrate. Analysis was performed by high pHanion exchange chromatography (HPAEC-PAD). A competitive transfer reaction ofcompound 1 in the presence of 3?-sialyllactose and N-acetyllactosamine showed abetter transference of Neu5Gc than of Neu5Ac.