Virulence of pathogenic organisms such as the Gram-positive Streptococcus pneumoniae is largely determined by the ability to degrade host glycoproteins and to metabolise the resultant carbohydrates. This family is the enzymatic region, EC:3.2.1.97, of the cell surface proteins that specifically cleave Gal-beta-1,3-GalNAc-alpha-Ser/Thr (T-antigen, galacto-N-biose), the core 1 type O-linked glycan common to mucin glycoproteins. This reaction is exemplified by the S. pneumoniae protein Swiss:B2DRU5, where Asp764 is the catalytic nucleophile-base and Glu796 the catalytic proton donor. This domain represents C-terminal the beta sandwich domain.

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