title: Unexpected properties of NADP-dependent secondary alcohol dehydrogenase (ADH-1) in Trichomonas vaginalis and other microaerophilic parasites.
abstract: Our previous observation that NADP-dependent secondary alcohol dehydrogenase (ADH-1) is down-regulated in metronidazole-resistant Trichomonas vaginalis isolates prompted us to further characterise the enzyme. In addition to its canonical enzyme activity as a secondary alcohol dehydrogenase, a pronounced, so far unknown, background NADPH-oxidising activity in absence of any added substrate was observed when the recombinant enzyme or T. vaginalis extract were used. This activity was strongly enhanced at low oxygen concentrations. Unexpectedly, all functions of ADH-1 were efficiently inhibited by coenzyme A which is a cofactor of a number of key enzymes in T. vaginalis metabolism, i.e. pyruvate:ferredoxin oxidoreductase (PFOR). These observations could be extended to Entamoeba histolytica and Tritrichomonas foetus, both of which have a homologue of ADH-1, but not to Giardia lamblia which lacks an NADP-dependent secondary alcohol dehydrogenase. Although we could not identify the substrate of the observed background activity, we propose that ADH-1 functions as a major sink for NADPH in microaerophilic parasites at low oxygen tension.
authors.affiliation: Institute of Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria. david.leitsch@meduniwien.ac.at
authors.forename: David
authors.initials: D
authors.lastname: Leitsch
authors.forename: Catrin F
authors.initials: CF
authors.lastname: Williams
authors.forename: David
authors.initials: D
authors.lastname: Lloyd
authors.forename: Michael
authors.initials: M
authors.lastname: Duchêne
mesh_terms: D019840:2-Propanol / Q000378:metabolism / Q000494:pharmacology; D000079:Acetaldehyde / Q000378:metabolism; D000096:Acetone / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003065:Coenzyme A / Q000494:pharmacology; D016054:DNA, Protozoan / Q000235:genetics; D004748:Entamoeba histolytica / Q000201:enzymology* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D016829:Giardia lamblia / Q000201:enzymology / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D014246:Trichomonas vaginalis / Q000201:enzymology* / Q000235:genetics; D016835:Tritrichomonas foetus / Q000201:enzymology* / Q000235:genetics
chemical_list: D016054:DNA, Protozoan; D011994:Recombinant Proteins; D000096:Acetone; D009249:NADP; D000429:Alcohol Oxidoreductases; C084155:alcohol dehydrogenase (NAD(P)+); D000079:Acetaldehyde; D019840:2-Propanol; D003065:Coenzyme A