Asparagine 405 of heparin lyase II prevents the cleavage of glycosidic linkages proximate to a 3-O-sulfoglucosamine residue.

Heparin and heparan sulfate contain a rare 3-O-sulfoglucosamine residue critical for anticoagulation and virus recognition, respectively. The glycosidic linkage proximate to this 3-O-sulfoglucosamine is resistant to cleavage by all heparin lyases (Heps). HepII has a broad specificity. The crystal structure of the wild type HepII identified its active site and showed a close spatial proximity between Asn405 and the 3-OH group of the bound glucosamine residue. In this study, we mutated Asn405 to the less sterically demanding Ala405 or Gly405, which broadened the substrate specificity of HepII and caused it to cleave the resistant linkage proximate to the 3-O-sulfoglucosamine residue.