Isolation and expression of an open reading frame encoding sialidase from Trypanosoma rangeli

Several protozoan parasites of human have been found to express enzymes capable of releasing terminal sialic acid residues from host glycans. These include enzymes similar in activity to bacterial and viral sialidases, as well as a novel type of enzyme, trans-sialidase, which can transfer sialic acid from one carbohydrate chain to another. Here we report the isolation of a gene and a gene fragment from the kinetoplastid Trypanosoma rangeli which encode products related in sequence to the trans-sialidase enzyme of T. cruzi. The gene fragment ORF is nearly identical to that of the complete gene, which encodes an enzymatically inactive protein. When the ORF of the gene fragment is fused to fragments from related genes, it encodes a product with sialidase activity. Both predicted T. rangeli protein products also have other potential structural features found in bacterial sialidases and in members of a previously described Trypanosoma trans-sialidase superfamily.