title: Donor and acceptor substrate selectivity among plant glycoside hydrolase family 32 enzymes.
abstract: Plant family 32 glycoside hydrolase enzymes include hydrolases (cell wall invertases, fructan exohydrolases, vacuolar invertases) and fructosyltransferases. These enzymes are very similar at the molecular and structural levels but are functionally different. Understanding the basis of the functional diversity in this family is a challenging task. By combining structural and site-directed mutagenesis data, Asp239 in AtcwINV1 was identified as an amino acid critical for binding and stabilizing sucrose. Plant fructan exohydrolases lack such an Asp239 equivalent. Substitution of Asp239 led to the loss of invertase activity, while its introduction in fructan exohydrolases increased invertase activity. Some fructan exohydrolases are inhibited by sucrose. The difference between the inhibitor (fructan exohydrolase) and the substrate (invertase) binding configurations of sucrose can be explained by the different orientation of Trp82. Furthermore, the evolutionary hydrolase/transferase transition could be mimicked and the difference between S-type fructosyltransferases (sucrose as donor) and F-type fructosyltransferases (fructan as donor) could be unravelled.
authors.affiliation: K.U.Leuven, Laboratory for Molecular Plant Physiology, Heverlee, Belgium. wim.vandenende@bio.kuleuven.be
authors.forename: Wim
authors.initials: W
authors.lastname: Van den Ende
authors.forename: Willem
authors.initials: W
authors.lastname: Lammens
authors.forename: André
authors.initials: A
authors.lastname: Van Laere
authors.forename: Lindsey
authors.initials: L
authors.lastname: Schroeven
authors.forename: Katrien
authors.initials: K
authors.lastname: Le Roy
mesh_terms: D000595:Amino Acid Sequence; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism; D043324:beta-Fructofuranosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D013395:Sucrose; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase