PMID: 9878409 , Related PDB ids: 1SLI, 2SLI, 3SLI, 4SLI

Authors:

Luo Y, Li SC, Li YT, Luo M

Title:

The 1.8 A structures of leech intramolecular trans-sialidase complexes: evidence of its enzymatic mechanism.

Journal:

J Mol Biol. 1999 Jan 8;285(1):323-32.

Abstract:

Intramolecular trans-sialidase from leech (Macrobdella decora) is the first member of the sialidase superfamily found to exhibit strict specificity towards the cleavage of terminal Neu5Acalpha2-->3Gal linkage in sialoglycoconjugates. Its release of 2,7-anhydro-Neu5Ac instead of Neu5Ac indicates that it catalyzes an intramolecular trans-sialosyl reaction. Crystal structures of its complexes with an inactive substrate analogue 2-propenyl-Neu5Ac, and with the product 2,7-anhydro-Neu5Ac, have been determined to 1.8 A resolution. The boat conformation of the pyranose observed in the complexes supports the proposed enzymatic mechanism that O7 of an axial 6-glycerol group attacks the positively charged C2 of the intermediate. A generalized mechanism is proposed for the sialidase superfamily.