%0 Journal Article %T Probing molecular function of trypanosomal sialidases: single point mutations can change substrate specificity and increase hydrolytic activity %+ Universidad Nacional de San Martin (UNSAM) %+ Biochimie Structurale %A Paris, Gaston %A Cremona, Maria, Laura %A Amaya, Maria, Fernanda %A Buschiazzo, Alejandro %A Giambiagi, Susana %A Frasch, Alberto, C C %A Alzari, Pedro, M %Z his work was supported by grants from the World Bank/UNDP/WHO Special Program for Research and Training in Tropical Diseases (TDR), ECOS-SeCyT (France-Argentina), the Institut Pasteur and the CNRS (France), the CONICET, the Agencia Nacional de Promoción Científica y Tecnológica and the Fundación Antorchas (Argentina). The research from ACCF was supported in part by an International Research Scholars Grant from the Howard Hughes Medical Institute. %< avec comité de lecture %@ 0959-6658 %J Glycobiology %I Oxford University Press (OUP) %V 11 %N 4 %P 305 - 311 %8 2001-04 %D 2001 %R 10.1093/glycob/11.4.305 %M 11358879 %Z Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM] %Z Chemical Sciences/Cristallography %Z Life Sciences [q-bio]/Microbiology and Parasitology/ParasitologyJournal articles %X Sialidases are present on the surface of several trypanoso-matid protozoan parasites. They are highly specific for sialic acid linked in α-(2,3) to a terminal β-galactose and include the strictly hydrolytic enzymes and trans-sialidases (sialyl-transferases). Based on the structural comparison of the sialidase from Trypanosoma rangeli and the trans-sialidase from T. cruzi (the agent of Chagas' disease in humans), we have explored the role of specific amino acid residues sought to be important for substrate specificity. The substitution of a conserved tryptophanyl residue in the two enzymes, Trp312/313-Ala, changed substrate specificity, rendering the point mutants capable to hydrolyze both α-(2,3)-and α-(2,6)-linked sialoconjugates. The same mutation abolished sialyl-transferase activity, indicating that transfer (but not hydrolysis) requires a precise orientation of the bound substrate. The exchange substitution of another residue that modulates oligosaccharide binding, Gln284-Pro, was found to significantly increase the hydrolytic activity of sialidase, and residue Tyr119 was confirmed to be part of a second binding site for the acceptor substrate in trans-sialidase. Together with the structural information, these results provide a consistent framework to account for the unique enzymatic properties of trypanosome trans-sialidases. %G English %L pasteur-02554090 %U https://pasteur.hal.science/pasteur-02554090 %~ PASTEUR %~ CNRS