title: The large subunit determines catalytic specificity of barley sucrose:fructan 6-fructosyltransferase and fescue sucrose:sucrose 1-fructosyltransferase.
abstract: Plant fructosyltransferases are highly homologous in primary sequence and typically consist of two subunits but catalyze widely different reactions. Using functional expression in the yeast Pichia pastoris, we show that the substrate specificity of festuca sucrose:sucrose 1--beta-D-fructosyltransferase (1-SST) and barley sucrose:fructan 6--beta-D-fructosyltransferase (6-SFT) is entirely determined by the large subunit. Chimeric enzymes with the large subunit of festuca 1-SST (LSuB) and the small subunit of barley 6-SFT have the same catalytic specificity as the native festuca 1-SST and vice versa. If the LSuB is expressed alone, it does not yield a functionally active enzyme, indicating that the small subunit is nevertheless essential.
authors.affiliation: Zurich Basel Plant Science Center, Botanisches Institut der Universität Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland.
authors.forename: Denise
authors.initials: D
authors.lastname: Altenbach
authors.forename: Eveline
authors.initials: E
authors.lastname: Nüesch
authors.forename: Alain D
authors.initials: AD
authors.lastname: Meyer
authors.forename: Thomas
authors.initials: T
authors.lastname: Boller
authors.forename: Andres
authors.initials: A
authors.lastname: Wiemken
mesh_terms: D020816:Amino Acid Motifs; D002384:Catalysis; D003001:Cloning, Molecular; D031751:Festuca / Q000201:enzymology*; D006602:Hexosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology*; D007661:Ketoses / Q000378:metabolism; D016296:Mutagenesis; D009844:Oligosaccharides / Q000378:metabolism; D010843:Pichia / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism; D001426:Bacterial Proteins
chemical_list: D006602:Hexosyltransferases; D007661:Ketoses; D009844:Oligosaccharides; D010940:Plant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D013395:Sucrose; C043600:fungitetraose; C097181:sucrose - fructan 6-fructosyltransferase; C021451:inulosucrase; D001426:Bacterial Proteins