Chitobiose Phosphorylase from Vibrio proteolyticus, a Member of Glycosyl Transferase Family 36, Has a Clan GH-L-like ( alpha / alpha ) sub(6) Barrel Fold

• Published in: Structure (London) Vol. 12; no. 6; pp. 937 - 947
• Main Authors: Hidaka, M, Honda, Y, Kitaoka, M, Nirasawa, S, Hayashi, K, Wakagi, T, Shoun, H, Fushinobu, S
• Format: Journal Article
• Language: English
• Published: 01.06.2004
• Subjects: Vibrio proteolyticus
• ISSN: 0969-2126
• DOI: 10.1016/j.str.2004.03.027

Vibrio proteolyticus chitobiose phosphorylase (ChBP) belongs to glycosyl transferase family 36 (GT-36), and catalyzes the reversible phosphorolysis of chitobiose into alpha -GlcNAc-1-phosphate and GlcNAc with inversion of the anomeric configuration. As the first known structures of a GT-36 enzyme, we determined the crystal structure of ChBP in a ternary complex with GlcNAc and SO sub(4). It is also the first structures of an inverting phosphorolytic enzyme in a complex with a sugar and a sulfate ion, and reveals a pseudo-ternary complex structure of enzyme-sugar-phosphate. ChBP comprises a beta sandwich domain and an ( alpha / alpha ) sub(6) barrel domain, constituting a distinctive structure among GT families. Instead, it shows significant structural similarity with glycoside hydrolase (GH) enzymes, glucoamylases (GH-15), and maltose phosphorylase (GH-65) in clan GH-L. The structural similarity reported here, together with distant sequence similarities between ChBP and GHs, led to the reclassification of family GT-36 into a novel GH family, namely GH-94.