, colominic acid and synthetic substrates. Sialidases may act as pathogenic factors in microbial infections. [ 6 ] The 1.8 A structure of trans-sialidase from leech (Macrobdella decora, Q27701 ) in complex with 2-deoxy-2, 3-didehydro-NeuAc was solved. The refined model comprising residues 81-769 has a catalytic beta-propeller domain, a N-terminal lectin