4kmi

Publication Abstract from PubMed

The crystal structure of a novel component of the mannan biodegradation system, 4-O-beta-d-mannosyl-d-glucose phosphorylase (MGP), was determined to a 1.68-A resolution. The structure of the enzyme revealed a unique homohexameric structure, which was formed by using two helices attached to the N-terminus and C-terminus as a tab for sticking between subunits. The structures of MGP complexes with genuine substrates, 4-O-beta-d-mannosyl-d-glucose and phosphate, and the product d-mannose-1-phosphate were also determined. The complex structures revealed that the invariant residue Asp131, which is supposed to be the general acid/base, did not exist close to the glycosidic Glc-O4 atom, which should be protonated in the catalytic reaction. Also, no solvent molecule that might mediate a proton transfer from Asp131 was observed in the substrate complex structure, suggesting that the catalytic mechanism of MGP is different from those of known disaccharide phosphorylases.

Structure of Novel Enzyme in Mannan Biodegradation Process 4-O-beta-d-Mannosyl-d-Glucose Phosphorylase MGP.,Nakae S, Ito S, Higa M, Senoura T, Wasaki J, Hijikata A, Shionyu M, Ito S, Shirai T J Mol Biol. 2013 Aug 14. pii: S0022-2836(13)00505-6. doi:, 10.1016/j.jmb.2013.08.002. PMID:23954514^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.