ENZYMATIC CHARACTERIZATION OF BETA-D-GALACTOSIDE ALPHA-2,3-TRANS-SIALIDASE FROM TRYPANOSOMA-CRUZI

The substrate specificity, physico-chemical, and kinetic properties of the trans-sialidase from Trypanosoma cruzi have been investigated. Th e enzyme demonstrates activity towards a wide range of saccharide, gly colipid, and glycoprotein acceptors which terminate with a beta-linked galactose residue, and synthesizes exclusively an alpha2-3 sialosidic linkage. Oligosaccharides which terminate in Galbeta1-4(Fucalpha1-3)G lcNAc, Galbeta1-3(Fucalpha1-4)GlcNAc, or Galalpha1- are not acceptor-s ubstrates. The enzyme utilizes alpha2,3-linked sialic acid when the do nor species is an oligosaccharide and can also transfer, at a low rate , sialic acid from synthetic alpha-sialosides such as p-nitrophenyl-al pha-N-acetylneuraminic acid, but NeuAcalpha2-3Galbeta1-4(Fucalpha1-3)G lc is not a donor-substrate. The trans-sialidase has an apparent pH op timum of 7.9 and a temperature optimum of 13-degrees-C. The kinetic pr operties of the enzyme suggest that the trans-sialylation reaction may occur via a rapid equilibrium random or steady-state ordered mechanis m. A method for immobilizing the enzyme is described together with exa mples of its use for the synthesis of oligosaccharide and glycoprotein precursors of sialyl-Lewis(a) and sialyl-Lewis(x).