Characterisation of the aldo keto reductase from helicobacter pylori.
Document Type Article
Aldo keto reductases reversibly reduce toxic aldehydes to their corresponding alcohol products. The aldo-keto reductase from Helicobacter pylori (HpAKR) was cloned and expressed in Escherichia coli as a His-tag fusion protein and purified using nickel chelate chromatography. The enzyme is a monomer with a molecular mass of approximately 39 kDa. It reduces a broad range of aldehyde substrates with a high catalytic efficiency and exhibits dual co-factor specificity for both NADH and NADPH. HpAKR can function over a broad pH range (pH 4-9) with a pH optimum of 5.5. Inhibition of AKR activity was observed with sodium valproate.
Generation of an isogenic HpAKR negative mutant of H. pylori demonstrated that HpAKR is required for growth under acidic conditions, suggesting a role in acid adaptation.
This study also examines the growth of a cinnamyl alcohol dehydrogenase (HpCAD) knockout mutant under acid conditions. It was surprising that despite previous reports that HpCAD is upregulated under acid growth conditions, that the knockout showed enhanced growth of acid pH.
Taken together these data indicate that these aldehyde metabolising enzymes may have an important role in H. pylori in acid adaptation in addition to their role as aldehyde metabolising enzymes.
Preliminary studies on a short chain alcohol dehydrogenase from H. pylori (HpSCADH) are also presented.