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 ability to efficiently carry out a sialyltransferase reaction using preformed glycoconjugates. The enzyme is predicted to have a multidomain structure, with one domain containing sequence and expected structural features found in bacterial sialidases. The trans-sialidase is very similar in overall sequence to another trypanosome enzyme that has only sialidase activity, Hybrid expression constructs containing pieces of these trypanosome trans-sialidase and sialidase genes were used to determine which regions of trans-sialidase are required for sialyltransferase activity. Two domains were found to influence the enzymatic activity: the N-terminal catalytic domain, and a downstream domain that resembles an Fn3-like module.