The large subunit determines catalytic specificity of barley sucrose:fructan 6-fructosyltransferase and fescue sucrose:sucrose 1-fructosyltransferase.
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.
Altenbach
Denise
D
Zurich Basel Plant Science Center, Botanisches Institut der Universität Basel, Hebelstrasse 1, CH-4056 Basel, Switzerland.
Nüesch
Eveline
E
Meyer
Alain D
AD
Boller
Thomas
T
Wiemken
Andres
A
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
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