Identification and characterization of hydroxyquinone hydratase activities from Sphingobium chlorophenolicum ATCC 39723

Abstract

Hydroxyquinol, a common metabolite of aromatic compounds, is readily auto-oxidized to hydroxyquinone. Enzymatic activities that metabolized hydroxyquinone were observed from the cell extracts of Sphingobium chlorophenolicum ATCC 39723. An enzyme capable of transforming hydroxyquinone was partially purified, and its activities were characterized. The end product was confirmed to be 2,5-dihydroxyquinone by comparing UV/Vis absorption spectra, electrospray mass spectra, and gas chromatography-mass spectra of the end product and the authentic compound. We have proposed that the enzyme adds a H2O molecule to hydroxyquinone to produce 2,5-dihydroxycyclohex-2-ene-1, 4-dione, which spontaneously rearranges to 1, 2,4,5-tetrahydroxybenzene. The latter is auto-oxidized by O2 to 2,5-dihydroxyquinone. The proposed pathway was supported by the overall reaction stoichiometry. Thus, the transformation of hydroxyquinol to 2,5-dihydroxyquinone involves two auto-oxidation of quinols and one enzymatic reaction catalyzed by a hydratase. The specific enzymatic step did not require O2, further supporting the assignment as a hydratase. To our knowledge, this is the first identification of a quinone hydratase, enhancing the knowledge on microbial metabolism of hydroxyquinone and possibly leading to the development of enzymatic method for the production of 2,5-dihydroxyquinone, a widely used chemical in various industrial applications.

para-Nitrophenol 4-monooxygenase and hydroxyquinol 1,2-dioxygenase catalyze sequential transformation of 4-nitrocatechol in Pseudomonas sp. strain WBC-3

“…3, together with consumption of NADPH (k max = 340 nm). There was also an increase in the absorbance at 260 nm, probably caused by the formation of hydroxyquinone (Chapman and Ribbons 1976;Bohuslavek et al 2005). Hydroxyquinone was generally thought to be reduced to hydroxyquinol in vivo by quinone reductases in a wide diversity of cells, such as broad-specific quinone reductase WrbA (Patridge and Ferry 2006) or NfsA (Zenno et al 1996) from E. coli, or some unidentified quinone Arrows indicate the direction of spectral changes reductases from the PNP uitlizer strain SAO101 (Kitagawa et al 2004).…”

Microbial degradation of chlorinated phenols

“…2,6-DCHQ is oxidized by 2,6-DCHQ 1,2-dioxygenase (PcpA) which requires O 2 and results in the formation 2-chloromaleylacetate as well as the liberation of one of the chloro groups as chloride (Ohtsubo et al 1999;Xu et al 1999;Xun et al 1999). Recently, a hydroxyquinone hydratase was discovered in Sphingobium chlorophenolicum which converts hydroxyl-1,4-quinone to 1,2,4,5-tetrahydroxybenzene, an intermediate that is subsequently auto-oxidized to 2,5-dihydroxyquinone in the presence of O 2 (Bohuslavek et al 2005). The hydratase may provide an alternative pathway of metabolizing the aromatic ring.…”

Reduction of Benzoquinones to Hydroquinones via Spontaneous Reaction with Glutathione and Enzymatic Reaction by S-Glutathionyl-Hydroquinone Reductases

“…HHQ (100−500 μM) was autoxidized to hydroxy-p-benzoquinone (HBQ) in 40 mM Tris buffer (pH 8) at 23 °C in about 15 min. 22 Excess (1 mM) GSH was then added to produce GS-HHQ, which occurred spontaneously and instantaneously. Immediately, NaBH 4 was added to 1 mM to prevent autoxidation of GS-HHQ.…”