The enzymatic hydrolysis of alpha-mannosides is catalyzed by glycoside hydrolases (GH), termed alpha-mannosidases. Streptococcal (Sp) GH38 alpha-mannosidase active on N-glycans and possibly O-glycans. SpGH38 structure can be considered as five domains: an N-terminal alpha/beta-domain, a three-helix bundle and three predominantly beta-sheet domains. This is the first of the three beta-sheet domains found in GH38, termed Beta-1. Structural analysis indicate that the beta-1 domain bows outward from the protein core, is involved in dimer interactions whilst also forming a lid 'above' and somewhat into the active centre of its dimer [1].

1: Structure and kinetic investigation of Streptococcus pyogenes family GH38 alpha-mannosidase. Suits MD, Zhu Y, Taylor EJ, Walton J, Zechel DL, Gilbert HJ, Davies GJ; PLoS One. 2010;5:e9006. PMID:20140249