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PubMedDate not supplied

The putative regulator of catechol catabolism in Rhodococcus opacus 1CP--an IclR-type, not a LysR-type transcriptional regulator.

The catechol catabolic genes catABC from Rhodococcus opacus 1CP have previously been characterized by sequence analysis of the insert cloned on plasmid pRER1. Now, a 5.1-kb DNA fragment which overlaps with the insert of pRER1 was cloned, yielding pRER2, and subjected to sequencing. Besides three other open reading frames, a gene was detected ca 200 bp upstream of the catechol 1,2-dioxygenase gene catA, which is obviously transcribed divergently from catABC. The protein which can be deduced from this gene, CatR, resembles members of the PobR subfamily of IclR-type regulatory proteins. This finding was unexpected, as all catechol and chlorocatechol gene clusters known thus far from proteobacteria are under control of LysR-type regulators. It was not possible to inactivate catR by homologous recombination. However, heterologously expressed CatR in vitro bound specifically to the intergenic region between catR and catA thereby providing a first indication for a possible involvement of CatR in the regulation of catechol catabolism.

Amino Acid Sequence↗
PubMed1980

Catechol-O-methyltransferase activity: a determinant of levodopa response.

In 14 patients with Parkinson's disease on long-term therapy the erythrocyte catechol-O-methyltransferase activity was found to correlate with the average plasma concentration ratio of 3-O-methyldopa to levodopa and with the fasting plasma concentration ratio of 3-O methyldopa to levodopa. Patients with the higher erythrocyte catechol-O-methyltransferase activities were those with less favorable clinical responses to levodopa. Since erythrocyte catechol-O-methyltransferase activity may reflect the activity of that enzyme in the major metabolizing tissues, catechol-O-methyltransferase activity would seem to be a significant determinant of response to levodopa.

Aged↗
PubMed1975

Properties of catechol O-methyltransferases from brain and liver of rat and human.

Kinetic and electrophoretic properties of catechol O-methyltransferases (EC 2.1.1.6) from brain and liver were studied. The enzyme of either rat or human tissues exhibited a single molecular form when subjected to electrophoresis at pH7.9. At pH9 a second, apparently oxidized, form was detected. Isoelectric-focusing experiments also indicated only one enzyme form, which was identical from extracts of brain and liver of each species (pI = 5.2 for rat, 5.5 for human). Similarities between brain and liver catechol O-methyltransferase of a given species were also demonstrated by kinetic parameters, meta/para ratios of products, and inhibitor potencies. Human catechol O-methyltransferase exhibited lower Km values than did the rat enzyme for S-adenosyl-L-methionine, dopamine and dihydroxybenzoic acid. Adrenochrome inhibited both rat and human enzyme. It was concluded (1) that only a single enzyme form could be demonstrated in the physiological pH region; (2) that catechol O-methyltransferase of brain could not be distinguished from the liver enzyme of the same species; and (3) that species differences exist between the enzymes of rat and human tissues.

Adrenochrome↗
PubMed2004

The role of the conserved residues His-246, His-199, and Tyr-255 in the catalysis of catechol 2,3-dioxygenase from Pseudomonas stutzeri OX1.

Catechol 2,3-dioxygenase (C2,3O) from Pseudomonas stutzeri OX1, which is able to grow on various aromatic substrates as the sole source of carbon and energy, has been expressed in Escherichia coli, purified, characterized, and found to be very similar to other dioxygenases from Pseudomonas species. Interestingly, the activity of the protein shows a rather unusual pH dependence when assayed on catechol. A model of the catalytic mechanism was developed that is able to reproduce the catalytic behavior of the protein as a function of the pH. The model includes multiple equilibria and four productive intermediates with different ionization states of the enzyme-substrate complex. The fitting of the theoretical curve to the experimental data suggests that a tyrosine and two histidine residues are involved in catalysis. Mutants (H246N)-, (H246A)-, (H199N)- and (Y255F)-C2,3O were produced to investigate the role of highly conserved His-199, His-246, and Tyr-255. The strongly reduced activity of the mutants suggests a primary catalytic role for each of these residues. Moreover, mutants at positions 199 and 246 display pH profiles different from that of the wild-type protein, thus indicating that residues His-246 and His-199 play a role in determining the unusual pH dependence of the enzyme. In addition, electron-withdrawing groups on catechol, which increase the acidity of the phenolic hydroxyl group, are able to counterbalance the effect of the mutation H246N in reducing catalytic activity but cause a further reduction of the activity of (H199N)-C2,3O. This finding suggests that His-246 is involved in the initial catechol deprotonation, whereas His-199 promotes the reaction between oxygen and the aromatic ring.

Binding Sites↗
PubMed1987

Covalent binding of estrogen metabolites to hamster liver microsomal proteins: inhibition by ascorbic acid and catechol-O-methyl transferase.

We have studied the irreversible binding of [14C]estradiol to hamster liver and kidney microsomes of castrated hamsters. The binding of estradiol metabolites to kidney microsomes was approximately 25 times lower than seen for liver microsomes, and was not affected by increases in protein or substrate concentration. Our results indicate that this irreversible binding, covalent in nature, is dependent on the metabolism of estrogens to catechols since the absence of NADPH markedly reduces this binding. The irreversible binding was inhibited nearly 70% by addition of catechol-O-methyl transferase (COMT) and S-adenosylmethionine (SAM). Ascorbic acid also inhibited the binding to 85% in a dose-dependent manner. Utilizing a displacement assay to assess the relative covalent binding of different stilbene and steroidal estrogens with homologous radiolabeled hormones, we found that only indenestrol B exhibited greater ability than diethylstilbestrol (DES) to displace [14C]DES from hepatic microsomal proteins. Except for hydroxypropiophenone and beta-dienestrol, all of the stilbene estrogens studied displaced the radioactive DES binding from these liver proteins to a greater extent than estradiol at comparable concentrations. A marked difference was observed in the ability of alpha- and beta-dienestrol to displace [14C]DES. Using radioinert steroidal estrogens to displace [14C]estradiol, we observed that both estriol and deoxoestrone were significantly less effective in displacing radiolabeled estradiol from liver microsomal proteins. Only ethinyl estradiol and 2-hydroxyestradiol displaced greater than 50% of the radioactive hormone at 1-fold excess concentrations. Interestingly, 11 beta-methoxyethinyl estradiol (Moxestrol) exhibited essentially the same ability to bind liver microsomal proteins as estradiol. When estrone and 2,4-dibromoestradiol were used as substrates together, we found the latter compound to be inactive as a substrate for estrogen hydroxylase (ESH) and additionally inhibited the metabolism of estrone to form the catechol metabolite. Data presented herein suggest that the chemically reactive estrogen metabolites responsible for covalent binding of both stilbene and steroidal estrogens are quinoids derived from catechols formed earlier in metabolism. Except for ethinyl estradiol which is a good substrate for liver, but not kidney microsomal ESH, the carcinogenicity data for the hamster kidney with respect to these estrogens is consistent with the covalent binding data presented.

Animals↗
PubMed1982

Rapid and sensitive single-step radiochemical assay for catechol-O-methyltransferase.

A simple, rapid and reliable radiometric assay for the determination of catechol-O-methyltransferase activity is described. The method is based on the conversion of catechol to [3H]guaiacol by catechol-O-methyltransferase in the presence of Mg2+, adenosine deaminase and S-adenosyl L-[methyl-3H]methionine. Incubation and direct extraction of [3H]guaiacol into organic scintillation fluid, as well as counting, are performed in the same standard scintillation vial. The assay is easy to perform and more sensitive than previous analogous procedures. The method has been applied to the assay of catechol-O-methyltransferase activity in discrete brain areas and also peripheral organs of rat and in human erythrocytes.

Adenosine Deaminase↗
PubMed1981

Inhibition of catechol 2,3-dioxygenase from Pseudomonas putida by 3-chlorocatechol.

Partially purified preparations of catechol 2,3-dioxygenase from toluene-grown cells of Pseudomonas putida catalyzed the stoichiometric oxidation of 3-methylcatechol to 2-hydroxy-6-oxohepta-2,4-dienoate. Other substrates oxidized by the enzyme preparation were catechol, 4-methylcatechol, and 4-fluorocatechol. The apparent Michaelis constants for 3-methylcatechol and catechol were 10.6 and 22.0 muM, respectively. Substitution at the 4-position decreases the affinity and activity of the enzyme for the substrate. Catechol 2,3-dioxygenase preparations did not oxidize 3-chlorocatechol. In addition, incubation of the enzyme with 3-chlorocatechol led to inactivation of the enzyme. Kinetic analyses revealed that both 3-chlorocatechol and 4-chlorocatechol were noncompetitive or mixed-type inhibitors of the enzyme. 3-Chlorocatechol (Ki = 0.14 muM) was a more potent inhibitor than 4-chlorocatechol (Ki = 50 muM). The effect of the ion-chelating agents Tiron and o-phenanthrolene were compared with that of 3-chlorocatechol on the inactivation of the enzyme. Each inhibitor appeared to remove iron from the enzyme, since inactive enzyme preparations could be fully reactivated by treatment with ferrous iron and a reducing agent.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed2002

Differential expression of two catechol 1,2-dioxygenases in Burkholderia sp. strain TH2.

Burkholderia sp. strain TH2, a 2-chlorobenzoate (2CB)-degrading bacterium, metabolizes benzoate (BA) and 2CB via catechol. Two different gene clusters for the catechol ortho-cleavage pathway (cat1 and cat2) were cloned from TH2 and analyzed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis showed that while both catechol dioxygenases (CatA1 and CatA2) were produced in BA-grown cells, CatA1 was undetectable when strain TH2 was grown on 2CB or cis,cis-muconate (CCM), an intermediate of catechol degradation. However, production of CatA1 during growth on 2CB or CCM was observed when cat2 genes were disrupted. The difference in the production of CatA1 and CatA2 was apparently due to a difference in inducer recognition by the regulators of the gene clusters. The inducer of CatA1 was found to be BA, not 2CB, by using a 2-halobenzoate dioxygenase gene (cbd) disruptant, which is incapable of transforming (chloro)benzoate. It was also found that CCM or its metabolite acts as an inducer for CatA2. When cat2 genes were disrupted, the growth rate in 2CB culture was reduced while that in BA culture was not. These results suggest that although cat2 genes are not indispensable for growth of TH2 on 2CB, they are advantageous.

Bacterial Proteins↗
PubMed2006

Specificity of catechol ortho-cleavage during para-toluate degradation by Rhodococcus opacus 1cp.

Degradation of para-toluate by Rhodococcus opacus 1cp was investigated. Activities of the key enzymes of this process, catechol 1,2-dioxygenase and muconate cycloisomerase, are detected in this microorganism. Growth on p-toluate was accompanied by induction of two catechol 1,2-dioxygenases. The substrate specificity and physicochemical properties of one enzyme are identical to those of chlorocatechol 1,2-dioxygenase; induction of the latter enzyme was observed during R. opacus 1cp growth on 4-chlorophenol. The other enzyme isolated from the biomass grown on p-toluate exhibited lower rate of chlorinated substrate cleavage compared to the catechol substrate. However, this enzyme is not identical to the catechol 1,2-dioxygenase cloned in this strain within the benzoate catabolism operon. This supports the hypothesis on the existence of multiple forms of dioxygenases as adaptive reactions of microorganisms in response to environmental stress.

Adaptation, Physiological↗
PubMed2000

DNA degradation by the mixture of copper and catechol is caused by DNA-copper-hydroperoxo complexes, probably DNA-Cu(I)OOH.

Free hydroxyl radicals (free (.)OH), singlet oxygen ((1)O(2)), or (. )OH produced by DNA-copper-hydroperoxo complexes are possible DNA-damaging reactive oxygen species (ROS) in the reaction system containing copper, catechol, and DNA. para-Chlorobenzoic acid (pCBA) degradation studies revealed that CuCl(2) mixed with catechol produced free (.)OH. In the presence of DNA, however, inhibition of the pCBA degradation suggested that another ROS is responsible for the DNA degradation. Of a series of ROS scavengers investigated, only KI, NaN(3), and Na-formate-all of the salts tested-strongly inhibited the DNA degradation, suggesting that the ionic strength rather than the reactivity of the individual scavengers could be responsible for the observed inhibition. The ionic strength effect was confirmed by increasing the concentration of phosphate buffer, which is a poor (.)OH scavenger, and was interpreted as the result of destabilization of DNA-copper-hydroperoxo complexes. Piperidine-labile site patterns in DNA degraded by copper and catechol showed that the mixture of Cu(II) and catechol degrades DNA via the intermediate formation of a DNA-copper-hydroperoxo complex. Replacement of guanine by 7-deazaguanine did not retard the DNA degradation, suggesting that the DNA-copper-hydroperoxo complexes do not bind to the guanine N-7 as proposed in the literature.

Catechols↗
PubMed1995

Cloning, DNA sequencing, and amino acid sequencing of catechol 1,2-dioxygenases (pyrocatechase) from Pseudomonas putida mt-2 and Pseudomonas arvilla C-1.

Catechol 1,2-dioxygenase catalyzes the oxygenative ring cleavage of catechol to form cis,cis-muconic acid and is encoded by a catA gene. We have cloned a catA gene from Pseudomonas putida mt-2 using a PCR product of amino acid sequence-based primers as a probe. The amino acid sequence deduced from the 930 nucleotides was in complete agreement with the chemically determined sequence of the protein. Crude extracts of Escherichia coli cells carrying the catA gene downstream from the lac promoter showed the enzyme activity. By using the same probe, we also cloned and sequenced the catA beta gene for catechol 1,2-dioxygenase isozyme beta beta from Pseudomonas arvilla C-1, which has three isozymes, alpha alpha, alpha beta, and beta beta (C. Nakai, H. Horiike, S. Kuramitsu, H. Kagamiyama, and M. Nozaki, 1990, J. Biol. Chem. 265, 660-665). There was very high homology between isozyme beta beta of the C-1 strain and the enzyme of the mt-2 strain in both the amino acid (98%) and the DNA sequences (97%). A preference for the use of codons terminating in C and G was found in the coding region of both the enzymes, which contributed to the high G + C content (65-66%) of the genes. A comparison of the DNA sequences of various catA genes from other sources revealed their common ancestry, whereas a comparison of the amino acid sequences of the enzymes revealed clear reflection of substrate specificity. Tyrosyl and histidyl residues for proposed ligands of ferric ion are conserved in all catechol 1,2-dioxygenases.

Amino Acid Sequence↗
PubMed1997

ESR identification of free radicals formed from the oxidation of catechol estrogens by Cu2+.

Catechol estrogens are genotoxic, indirectly through redox cycling mechanisms leading to oxidative DNA damage and directly by formation of quinone-DNA adducts. Previously, we demonstrated that Cu2+ can oxidize estradiol (E2) catechols, establishing a copper redox cycle leading to the formation of DNA strand breaks. The goal of this study was to use electron spin resonance techniques to identify the free radical intermediates formed. The 2- and 4-OH catechols of E2 and ethinyl estradiol (EE) were oxidized to semiquinone intermediates, stabilized by Mg2+, when incubated with Cu2+. The 4-OH-EE semiquinone decayed more slowly than the 2-OH-EE semiquinone. Using the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone, 4-OH-E2 plus Cu2+ generated hydroxyl radicals at a greater rate than 2-OH-E2 plus Cu2+. Formation of hydroxyl and methyl radical adducts was detected, using 5,5-dimethyl-1-pyrroline-N-oxide as the spin trap, when 2-OH-E2 was incubated with Cu2+ and 1% dimethyl sulfoxide. This was inhibited by the Cu1+ chelator bathocuproinedisulfonic acid and catalase. These data demonstrate that the oxidation of estrogen catechols by Cu2+ leads to a Cu-dependent mechanism of hydroxyl radical production via a hydrogen peroxide intermediate and suggest a mechanism for estrogen-associated site-specific DNA damage and mutagenesis.

Benzoquinones↗
PubMed1999

Mass spectrometric analysis of catechol-histidine adducts from insect cuticle.

Adducts of catechols and histidine, which are produced by reactions of 1,2-quinones and p-quinone methides with histidyl residues in proteins incorporated into the insect exoskeleton, were characterized using electrospray ionization mass spectrometry (ESMS), tandem electrospray mass spectrometry (ESMS-MS, collision-induced dissociation), and ion trap mass spectrometry (ITMS). Compounds examined included adducts obtained from acid hydrolysates of Manduca sexta (tobacco hornworm) pupal cuticle exuviae and products obtained from model reactions under defined conditions. The ESMS and ITMS spectra of 6-(N-3')-histidyldopamine [6-(N-3')-His-DA, pi isomer] isolated from M. sexta cuticle were dominated by a [M + H]+ ion at m/z 308, rather than the expected m/z 307. High-resolution fast atom bombardment MS yielded an empirical formula of C14H18N3O5, which was consistent with this compound being 6-(N-1')-histidyl-2-(3, 4-dihydroxyphenyl)ethanol [6-(N-1')-His-DOPET] instead of a DA adduct. Similar results were obtained when histidyl-catechol compounds linked at C-7 of the catechol were examined; the (N-1') isomer was confirmed as a DA adduct, and the (N-3') isomer identified as an (N-1')-DOPET derivative. Direct MS analysis of unfractionated cuticle hydrolysate revealed intense parent and product ions characteristic of 6- and 7-linked adducts of histidine and DOPET. Mass spectrometric analysis of model adducts synthesized by electrochemical oxidative coupling of N-acetyldopamine (NADA) quinone and N-acetylhistidine (NAcH) identified the point of attachment in the two isomers. A prominent product ion corresponding to loss of CO2 from [M + H]+ of 2-NAcH-NADA confirmed this as being the (N-3') isomer. Loss of (H2O + CO) from 6-NAcH-NADA suggested that this adduct was the (N-1') isomer. The results support the hypothesis that insect cuticle sclerotization involves the formation of C-N cross-links between histidine residues in cuticular proteins, and both ring and side-chain carbons of three catechols: NADA, N-beta-alanyldopamine, and DOPET.

Animals↗
PubMed1998

Structure of catechol 2,3-dioxygenase gene from Alcaligenes eutrophus 335.

Catechol 2,3-dioxygenase (C23O), one of extradiol-type dioxygenases cleaving aromatic C-C bond at meta position of dihydroxylated aromatic substrates, catalyzes the conversion of catechol to 2-hydroxymuconic semialdehyde. As our ongoing study to characterize biochemical and genetic properties of the extradiol-type dioxygenases at molecular level, a C23O gene encoded in chromosomal DNA of Alcaligenes eutrophus 335, a strain degrading phenol and p-cresol, was cloned. The C23O gene was localized in an 1.4-kb PstI fragment from A. eutrophus 335, and was expressed in E. coli HB101. The C23O exhibited the highest aromatic ring-fission activity to catechol as a substrate, and its relative activity to other dihydroxylated aromatic substrates was in order of catechol >> 4-methylcatechol > 3-methylcatechol, protocatechuate, 4-chlorocatechol > 3,4-dihydroxy-phenylacetate > 2,3-dihydroxybiphenyl. Nucleotide sequence of the 1.4-kb fragment has revealed that an open reading frame (ORF) corresponding to the C23O gene was composed of 930 base pairs. A putative ribosome-binding sequence of AGGAG was found at about 10 nucleotides upstream the ORF which can encode a polypeptide of molecular weight 34 kDa consisting of 309 amino acid residues. The deduced amino acid sequence of C23O from A. eutrophus 335 exhibited the highest 59% identity with those of corresponding enzymes from Pseudomonas sp. CF600 (p VI150), P. putida HS1 (pDK1), and P. putida PpG7 (NAH7). An alignment of amino acid sequences of extradiol-type dioxygenases including C23O from A. eutrophus 335 has revealed that catalytically and structurally important amino acid residues of the enzymes were conserved during evolution.

Alcaligenes↗
PubMed1999

Utilization of phenoxyacetic acid, by strains using either the ortho or meta cleavage of catechol during phenol degradation, after conjugal transfer of tfdA, the gene encoding a 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase.

The degradation of recalcitrant pollutants in contaminated soils and waters could be facilitated by broadening the degradative capabilities of indigenous microbes by the conjugal transfer of catabolic genes. The feasibility of establishing bacterial populations that degrade phenoxyacetic acid by conjugal transfer of tfdA, the gene encoding 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase, to phenol-degrading strains of Pseudomonas and Ralstonia was examined. The mobilizable plasmid pKJS32 served as a vector for delivery of tfdA and the regulatory gene, tfdS. Transconjugant strains that degraded phenol by an ortho cleavage of catechol grew well on phenoxyacetic acid while those employing a meta cleavage could only grow on phenoxyacetic acid in the presence of benzoic acid or after a prolonged lag period and the appearance of mutants that had gained catechol 1,2-dioxygenase activities. Thus, an ortho cleavage of catechol was essential for degradation of phenoxyacetic acid, suggesting that a product of the ortho-cleavage pathway, probably cis, cis-muconic acid, is an inducer of tfdA gene expression. Establishment of phenoxyacetic-acid-degrading soil populations by conjugal transfer of tfdA would depend on the presence of phenol-degrading recipients employing an ortho cleavage of catechol.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2004

The catalytic cycle of catechol oxidase.

Hybrid density functional theory with the B3LYP functional has been used to investigate the catalytic mechanism of catechol oxidase. Catechol oxidase belongs to a class of enzymes that has a copper dimer with histidine ligands at the active site. Another member of this class is tyrosinase, which has been studied by similar methods previously. An important advantage for the present study compared to the one for tyrosinase is that X-ray crystal structures exist for catechol oxidase. The most critical step in the mechanism for catechol oxidase is where the peroxide O-O bond is cleaved. In the suggested mechanism this cleavage occurs in concert with a proton transfer from the substrate. Shortly after the transition state is passed there is another proton transfer from the substrate, which completes the formation of a water molecule. An important feature of the mechanism, like the one for tyrosinase, is that no proton transfers to or from residues outside the metal complex are needed. The calculated energetics is in reasonable agreement with experiments. Comparisons are made to other similar enzymes studied previously.

Binding Sites↗
PubMed1999

Catechol 2,3-dioxygenase from the thermophilic, phenol-degrading Bacillus thermoleovorans strain A2 has unexpected low thermal stability.

Catechol 2,3-dioxygenase from the thermophilic Bacillus thermoleovorans A2 was purified and characterized. The catechol 2,3-dioxygenase has a molecular mass of 135000Da and consists of four identical subunits of 34 700 Da. One iron per enzyme subunit was detected using atom absorption spectroscopy. Enzyme activity was not inhibited by EDTA, suggesting that the iron is tightly bound. Addition of hydrogen peroxide to the enzyme completely destroyed activity, indicating that the iron was in the divalent state. The isoelectric point of the enzyme was 4.8. The enzyme displayed optimal activity at pH 7.2 and 70 degrees C. The half-life of the catechol 2,3-dioxygenase at the optimum temperature was 1.5 min under aerobic conditions and 10min in a nitrogen atmosphere. This stability of the enzyme is comparable to the stability of the enzyme from the mesophilic Pseudomonas putida mt-2. The stability of the cloned enzyme in E. coli extracts was identical to the stability in wild-type extracts, suggesting that no stabilizing factors were present in Bacillus thermoleovorans A2 In whole cells the half-life of the enzyme at 70 degrees C was approximately 26min, when protein synthesis was disrupted by chloramphenicol; however, the activity remained constant when protein synthesis was not inhibited. From these results we concluded that catechol 2,3-dioxygenase from Bacillus thermoleovorans A2 is not particularly thermostable, but that the organism retains the ability to degrade phenol at high temperatures because of continuous production of this enzyme.

Bacillus↗
PubMed2004

Evidence for the existence of PAH-quinone reductase and catechol-O-methyltransferase in Mycobacterium vanbaalenii PYR-1.

Polycyclic aromatic hydrocarbon (PAH) quinone reductase (PQR) and catechol-O-methyltransferase (COMT), from the PAH-degrading Mycobacterium vanbaalenii PYR-1, were demonstrated to be constitutive enzymes located in the soluble fraction of cell extracts. PQR activities for the reduction of 9,10-phenanthrenequinone and 4,5-pyrene- quinone were 1.40+/-0.13 and 0.12+/-0.01 micromol min(-1) mg-protein(-1), respectively. The exogenous catechols alizarin, anthrarobin, 2,3-dihydroxynaphthalene and esculetin inhibited PQR activity. Anthrarobin (100 microM) and esculetin (100 microM) inhibited 4,5-pyrenequinone reduction by 64-92%. COMT was involved in the O-methylation of 1,2-dihydroxyphenanthrene to form 1-methoxy-2-hydroxyphenanthrene and 1,2-dimethoxyphenanthrene. Both pyrene and 1-hydroxypyrene were metabolized by M. vanbaalenii PYR-1 to form 1-methoxypyrene, 1-methoxy-2-hydroxypyrene, 1-hydroxy-2-methoxypyrene and 1,2-dimethoxypyrene. Among the catechols tested, anthrarobin showed the highest COMT activity (1.06+/-0.04 nmol/30 min(-1) mg-protein(-1)). These results suggest that the PQR and COMT activities of M. vanbaalenii PYR-1 may play an important role in the detoxification of PAH catechols.

Biotransformation↗