The trans-sialidase from Trypanosoma cruzi efficiently transfers alpha-(2-->3)-linked N-glycolylneuraminic acid to terminal beta-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(alpha2-->3)Gal(beta1-->4)GlcbetaOCH(2)CH(2)N(3) (1) and Neu5Gc(alpha2-->3)Gal(beta1-->3)GlcNAcbetaOCH(2)CH(2)N(3) (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.
Agustí
Rosalía
R
CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
Giorgi
María Eugenia
ME
de Lederkremer
Rosa M
RM
D000818:Animals; D005690:Galactose / Q000737:chemistry* / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D009438:Neuraminic Acids / Q000737:chemistry* / Q000378:metabolism*; D009439:Neuraminidase / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000201:enzymology*
D006023:Glycoproteins; D009438:Neuraminic Acids; C032592:N-glycolylneuraminic acid; C069715:trans-sialidase; D009439:Neuraminidase; D005690:Galactose