title: Hydroxyhydroquinone reductase, the initial enzyme involved in the degradation of hydroxyhydroquinone (1,2,4-trihydroxybenzene) by Desulfovibrio inopinatus.
abstract: The recently isolated sulfate reducer Desulfovibrio inopinatus oxidizes hydroxyhydroquinone (1,2,4trihydroxybenzene; HHQ) to 2 mol acetate and 2 mol CO2 (mol substrate)-1, with stoichiometric reduction of sulfate to sulfide. None of the key enzymes of fermentative HHQ degradation, i.e. HHQ-1,2,3,5-tetrahydroxybenzene transhydroxylase or phloroglucinol reductase, were detected in cell-free extracts of D. inopinatus, indicating that this bacterium uses a different pathway for anaerobic HHQ degradation. HHQ was reduced with NADH in cell-free extracts to a nonaromatic compound, which was identified as dihydrohydroxyhydroquinone by its retention time in HPLC separation and by HPLC-mass spectrometry. The compound was identical with the product of chemical reduction of HHQ with sodium borohydride. Dihydrohydroxyhydroquinone was converted stoichiometrically to acetate and to an unknown coproduct. HHQ reduction was an enzymatic activity which was present in the cell-free extract at 0.25-0.30 U (mg protein)-1, with a pH optimum at 7.5. The enzyme was sensitive to sodium chloride, potassium chloride, EDTA, and o-phenanthroline, and exhibited little sensitivity towards sulfhydryl group reagents, such as copper chloride or p-chloromercuribenzoate.
authors.affiliation: Fakultät für Biologie, Universität Konstanz, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Reichenbecher
authors.forename: B
authors.initials: B
authors.lastname: Philipp
authors.forename: M J
authors.initials: MJ
authors.lastname: Suter
authors.forename: B
authors.initials: B
authors.lastname: Schink
mesh_terms: D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid; D003901:Desulfovibrio / Q000201:enzymology*; D004795:Enzyme Stability; D006873:Hydroquinones / Q000378:metabolism*; D013058:Mass Spectrometry; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D044925:Oxidoreductases Acting on CH-CH Group Donors; D011808:Quinone Reductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism
chemical_list: D006873:Hydroquinones; D013431:Sulfates; C410844:dihydrohydroxyhydroquinone; C013038:hydroxyhydroquinone; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C058829:phloroglucinol reductase; D011808:Quinone Reductases; C410843:hydroxyhydroquinone reductase