The trans-sialidase from the African trypanosome Trypanosoma brucei.

GEORGINA N. MONTAGNA; GASTON PARIS; MARIA L. CREMONA; MARIA F. AMAYA; ALEJANDRO BUSCHIAZZO; PEDRO ALZARI; ALBERTO C.C. FRASCH

FEBS JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2002

1742-464X

Trypanosoma brucei is the cause of the diseases known as sleeping sickness in humans(T. brucei ssp. gambiense and ssp. rhodesiense) and ngana in domestic animals (T. bruceibrucei) in Africa. Procyclic trypomastigotes, the tsetse vector stage, express a surfaceboundtrans-sialidase that transfers sialic acid to the glycosylphosphatidylinositol anchorof procyclin, a surface glycoprotein covering the parasite surface. Trans-sialidase is aunique enzyme expressed by a few trypanosomatids that allows them to scavenge sialicacid from sialylated compounds present in the infected host. The only enzymeextensively characterized is that of the American trypanosome T. cruzi (TcTS). In thiswork we identified and characterized the gene encoding the trans-sialidase from T. bruceibrucei (TbTS). TbTS genes are present at a small copy number, at variance withAmerican trypanosomes where a large gene family is present. The recombinant TbTSprotein has both sialidase and trans-sialidase activity, but it is about 10 times moreefficient in transferring than in hydrolysing sialic acid. Its N-terminus contains a regionof 372 amino acids that is 45% identical to the catalytic domain of TcTS and contains therelevant residues required for catalysis. The enzymatic activity of mutants at keypositions involved in the transfer reaction revealed that the catalytic sites of TcTS andTbTS are likely to be similar, but are not identical. As in the case of TcTS and TrSA, thesubstitution of a conserved tryptophanyl residue changed the substrate specificityrendering a mutant protein capable of hydrolysing both alpha-(2,3) and alpha-(2,6)-linkedsialoconjugates.12 Impairment of cellular redox