Directed mutagenesis of the Trypanosoma cruzi trans-sialidase enzyme identifies two domains involved in its sialyltransferase activity

Of the increasing number of sialidases found to be made by microorganisms,the trypanosome trans-sialidase is unique in its added abilityto efficiently carry out a sialyltransferase reaction usingpreformed glymonjugates. The enzyme is predicted to have a multidomainstructure, with one domain containing sequence and expectedstructural features found in bacterial sialidases. The trans-sialidaseis very similar in overall sequence to another trypanosome enzymethat has only sialidase activity. Hybrid expression constructscontaining pieces of these trypanosome transsialidase and sialidasegenes were used to determine which regions of trans-sialidaseare required for sialyltransferase activity. Two domains werefound to influence the enzymatic activity: the N-terminal catalyticdomain, and a downstream domain that resembles an Fn3-like module. mutagenesis enzyme sialyltransferase trypanosome