Functional diversity in the trans-sialidase and mucin families in Trypanosoma cruzi.

Trypanosomes are unable to synthesize the monosaccharide sialic acid, but some African trypanosomes and the American Trypanosoma cruzi can incorporate sialic acid derived from the host. To do so, T. cruzi expresses a trans-sialidase, an enzyme that catalyzes the transfer of sialic acid from host glycoconjugates to mucin-like molecules located on the parasite surface membrane. The importance of the process is indicated by the fact that T. cruzi has hundreds of genes encoding trans-sialidase, trans-sialidase-like proteins and mucin core proteins. Sequence divergence of members of these families has resulted in some molecules having functions unrelated to the acquisition of sialic acid. In this article, Alberto Frasch reviews the structure and possible function of the proteins making up these families.