title: Different specificities of two aldehyde dehydrogenases fromSaccharomyces cerevisiae var. boulardii.
abstract: Aldehyde dehydrogenases play crucial roles in the detoxification of exogenous and endogenous aldehydes by catalysing their oxidation to carboxylic acid counterparts. The present study reports characterization of two such isoenzymes from the yeastSaccharomyces cerevisiae var. boulardii(NCYC 3264), one mitochondrial (Ald4p) and one cytosolic (Ald6p). Both Ald4p and Ald6p were oligomeric in solution and demonstrated positive kinetic cooperativity towards aldehyde substrates. Wild-type Ald6p showed activity only with aliphatic aldehydes. Ald4p, on the contrary, showed activity with benzaldehyde along with a limited range of aliphatic aldehydes. Inspection of modelled structure of Ald6p revealed that a bulky amino acid residue (Met177, compared with the equivalent residue Leu196in Ald4p) might cause steric hindrance of cyclic substrates. Therefore, we hypothesized that specificities of the two isoenzymes towards aldehyde substrates were partly driven by steric hindrance in the active site. A variant of wild-type Ald6p with the Met177residue replaced by a valine was also characterized to address to the hypothesis. It showed an increased specificity range and a gain of activity towards cyclohexanecarboxaldehyde. It also demonstrated an increased thermal stability when compared with both the wild-types. These data suggest that steric bulk in the active site of yeast aldehyde dehydrogenases is partially responsible for controlling specificity.
authors.affiliation: Department of Food Engineering and Technology, Institute of Chemical Technology (ICT), Matunga, Mumbai 400 019, India.|School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, U.K.
authors.forename: Suprama
authors.initials: S
authors.lastname: Datta
authors.affiliation: Department of Food Engineering and Technology, Institute of Chemical Technology (ICT), Matunga, Mumbai 400 019, India.
authors.forename: Uday S
authors.initials: US
authors.lastname: Annapure
authors.affiliation: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, U.K. d.timson@brighton.ac.uk.|School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Lewes Road, Brighton BN2 4GJ, U.K.
authors.forename: David J
authors.initials: DJ
authors.lastname: Timson
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism; D001547:Benzaldehydes / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D000069983:Saccharomyces boulardii / Q000201:enzymology* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism*; D013379:Substrate Specificity / Q000502:physiology
chemical_list: D000447:Aldehydes; D001547:Benzaldehydes; D005656:Fungal Proteins; D007527:Isoenzymes; D000444:Aldehyde Dehydrogenase; C032175:benzaldehyde
keywords: Yeast aldehyde dehydrogenase; aliphatic aldehyde; aromatic aldehyde; cooperative kinetics; enzyme specificity; tetrameric protein