Mee Blanaid, Kelleher Dermot, Frias Jesus, Malone Renee, Tipton Keith F, Henehan Gary T M, Windle Henry J
School of Food Science and Environmental Health, Dublin Institute of Technology, Ireland.
FEBS J. 2005 Mar;272(5):1255-64. doi: 10.1111/j.1742-4658.2005.04561.x.
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.
肉桂醇脱氢酶（CAD；1.1.1.195）催化对羟基肉桂醛可逆转化为其相应的醇，从而导致植物中木质素的生物合成。在植物之外，它们的作用尚不太明确。幽门螺杆菌肉桂醇脱氢酶基因（HpCAD）在大肠杆菌中克隆，并对重组酶的底物特异性进行了表征。该酶是一种42.5 kDa的单体，主要存在于细菌的胞质溶胶中。它对NADP（H）作为辅因子具有特异性，对醇和醛底物具有广泛的底物特异性。其底物特异性与已充分表征的植物酶相似。观察到高底物抑制作用，并提出了竞争性抑制机制。发现该酶能够催化苯甲醛歧化为苯甲醇和苯甲酸。这种歧化反应以前尚未在这类醇脱氢酶中得到证明，它为细菌提供了一种降低细胞内醛浓度的方法。
