title: Characterization of cinnamyl alcohol dehydrogenase of Helicobacter pylori. An aldehyde dismutating enzyme.
abstract: Cinnamyl alcohol dehydrogenases (CAD; 1.1.1.195) catalyse the reversible conversion of p-hydroxycinnamaldehydes to their corresponding alcohols, leading to the biosynthesis of lignin in plants. Outside of plants their role is less defined. The gene for cinnamyl alcohol dehydrogenase from Helicobacter pylori (HpCAD) was cloned in Escherichia coli and the recombinant enzyme characterized for substrate specificity. The enzyme is a monomer of 42.5 kDa found predominantly in the cytosol of the bacterium. It is specific for NADP(H) as cofactor and has a broad substrate specificity for alcohol and aldehyde substrates. Its substrate specificity is similar to the well-characterized plant enzymes. High substrate inhibition was observed and a mechanism of competitive inhibition proposed. The enzyme was found to be capable of catalysing the dismutation of benzaldehyde to benzyl alcohol and benzoic acid. This dismutation reaction has not been shown previously for this class of alcohol dehydrogenase and provides the bacterium with a means of reducing aldehyde concentration within the cell.
authors.affiliation: School of Food Science and Environmental Health, Dublin Institute of Technology, Ireland.
authors.forename: Blanaid
authors.initials: B
authors.lastname: Mee
authors.forename: Dermot
authors.initials: D
authors.lastname: Kelleher
authors.forename: Jesus
authors.initials: J
authors.lastname: Frias
authors.forename: Renee
authors.initials: R
authors.lastname: Malone
authors.forename: Keith F
authors.initials: KF
authors.lastname: Tipton
authors.forename: Gary T M
authors.initials: GT
authors.lastname: Henehan
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Windle
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism*; D019905:Benzyl Alcohol / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D003001:Cloning, Molecular; D016480:Helicobacter pylori / Q000201:enzymology*; D007700:Kinetics; D009249:NADP; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013347:Subcellular Fractions; D013379:Substrate Specificity
chemical_list: D001547:Benzaldehydes; D011994:Recombinant Proteins; D009249:NADP; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase; D019905:Benzyl Alcohol; C032175:benzaldehyde