title: Functions, structures, and applications of cellobiose 2-epimerase and glycoside hydrolase family 130 mannoside phosphorylases.
abstract: Carbohydrate isomerases/epimerases are essential in carbohydrate metabolism, and have great potential in industrial carbohydrate conversion. Cellobiose 2-epimerase (CE) reversibly epimerizes the reducing end d-glucose residue of β-(1→4)-linked disaccharides to d-mannose residue. CE shares catalytic machinery with monosaccharide isomerases and epimerases having an (α/α)6-barrel catalytic domain. Two histidine residues act as general acid and base catalysts in the proton abstraction and addition mechanism. β-Mannoside hydrolase and 4-O-β-d-mannosyl-d-glucose phosphorylase (MGP) were found as neighboring genes of CE, meaning that CE is involved in β-mannan metabolism, where it epimerizes β-d-mannopyranosyl-(1→4)-d-mannose to β-d-mannopyranosyl-(1→4)-d-glucose for further phosphorolysis. MGPs form glycoside hydrolase family 130 (GH130) together with other β-mannoside phosphorylases and hydrolases. Structural analysis of GH130 enzymes revealed an unusual catalytic mechanism involving a proton relay and the molecular basis for substrate and reaction specificities. Epilactose, efficiently produced from lactose using CE, has superior physiological functions as a prebiotic oligosaccharide.
authors.affiliation: a Research Faculty of Agriculture , Hokkaido University , Sapporo , Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Saburi
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001441:Bacteroides fragilis / Q000201:enzymology* / Q000235:genetics; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D020134:Catalytic Domain; D002475:Cellobiose / Q000737:chemistry / Q000378:metabolism; D020633:Cellvibrio / Q000201:enzymology* / Q000235:genetics; D004187:Disaccharides / Q000737:chemistry / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D008358:Mannose / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D011522:Protons; D013379:Substrate Specificity; D044902:beta-Mannosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D004187:Disaccharides; D011522:Protons; D002475:Cellobiose; C047464:epilactose; D009713:Nucleotidyltransferases; D044902:beta-Mannosidase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; D005947:Glucose; D008358:Mannose
keywords: 4-O-β-d-mannosyl-d-glucose phosphorylase; cellobiose 2-epimerase; epilactose; glycoside hydrolase family 130; β-1,4-mannooligosaccharide phosphorylase