Catechol degradation

Pure cultures growing anaerobically with catechol and sulfate were isolated,and the carboxylation of catechol was proposed to be the initial reaction of anaerobic catechol degradation by Desulfobacterium sp. strain Cat2. Zhang and Young" proposed that the initial key reaction for anaerobic degradation of naphthalene and phenanthrene was also carboxylation. 

Leppik R A (1989) Steroid catechol degradation disecoandrostane intermediates accumulated by Pseudomonas transposon mutant strains. J Gen Microbiol 135 1979-1988. 

A chlorophenoxyacetate-degrading Arthrobacter sp. contained an enzyme, which converted 2,4-dichlorophenol and other chlorophenols to catechols. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) and Oj were required for the reaction. The enzyme hydroaylating 2,4-dichlorophenol was partially separated from the catechol-degrading enzyme present in the bacterial extract. The compotmds formed from... 

Murakami S, Takashima A, Takemoto J, Takenaka S, Shinke R, Aoki K (1999) Cloning and sequence analysis of two catechol-degrading gene dusters from the aniline-assimilating bacterium Frateuria species ANA-18. Gene 226 189-198... 

Differences in growth phase can influence metal uptake in batch-cultured bacteria. Germanium uptake by Pseudomonas putida occurs in a biphasic pattern in a catechol-enriched medium the second uptake phase corresponds to catechol degradation, products of which facilitate germanium transport into cells [35]. 

Fig. 7. Photocatalyzed degradation of phenol showiag principal iatermediates including catechol [120-80-9] (1), hydroquiaoae [123-31 -9] (2), -beazoquiaoae [106-51-4] (3), pyrogaHol [87-66-1] (4), hydroxyhydroquiaoae [533-73-3] (5), and hydroxybenzoquiaone [2474-72-8] (6). The dashed lines...

Modulation of second-messenger pathways is also an attractive target upon which to base novel antidepressants. Rolipram [61413-54-5] an antidepressant in the preregistration phase, enhances the effects of noradrenaline though selective inhibition of central phosphodiesterase, an enzyme which degrades cycHc adenosiae monophosphate (cAMP). Modulation of the phosphatidyl iaositol second-messenger system coupled to, for example, 5-HT,, 5-HT,3, or 5-HT2( receptors might also lead to novel antidepressants, as well as to alternatives to lithium for treatment of mania. Novel compounds such as inhibitors of A-adenosyl-methionine or central catechol-0-methyltransferase also warrant attention. 

After reuptake into the cytosol, some noradrenaline may be taken up into the storage vesicles by the vesicular transporter and stored in the vesicles for subsequent release (see above). However, it is thought that the majority is broken down within the cytosol of the nerve terminal by monoamine oxidase (MAO ECl.4.3.4). A second degradative enzyme, catechol-O-methyl transferase (COMT EC2.1.1.6), is found mostly in nonneuronal tissues, such as smooth muscle, endothelial cells or glia. The metabolic pathway for noradrenaline follows a complex sequence of alternatives because the metabolic product of each of these enzymes can act as a substrate for the other (Fig 8.8). This could enable one of these enzymes to compensate for a deficiency in the other to some extent. 

The degradation of 4-chlorobiphenyl by Sphingomonas paucimobilis strain BPSl-3 formed the intermediates 4-chlorobenzoate and 4-chlorocatechol. Fission products from the catechol reacted with NH4+ to produce chloropyridine carboxylates (Davison et al. 1996) (Figure 2.2c). 

Rhizobia. Taxa belonging to both the genera Rhizobium and Bradyrhizobium are capable of degrading simple aromatic compounds including benzoate (Chen et al. 1984) and 4-hydroxy-benzoate (Parke and Omston 1986 Parke et al. 1991). It has been shown that 4-hydroxyben-zoate hydroxylase is required for the transport of 4-hydroxybenzoate into the cell (Wong et al. 1994). In strains of Rhizobium trifolium, the metabolism of benzoate involves either 3,4-dihydroxybenzoate (protocatechuate) 3,4-dioxygenase (Chen et al. 1984), or catechol... 

Degradation of the products of hydroxylation then involves fission of the catechols (or 2,5-dihydroxybenzoates) that are produced. All three fission pathways have been observed for 3,4-dihydroxybenzoate ... 

Salicylate is an intermediate in the metabolism of PAHs including naphthalene and phen-anthrene, and its degradation involves oxidation to catechol. The hydroxylase (monooxygenase) has been extensively studied (references in White-Stevens and Kamin 1972) and in the presence of an analog that does not serve as a substrate, NADH is oxidized with the production of H2O2 (White-Stevens and Kamin 1972). This uncoupling is characteristic of flavoenzymes and is exemplified also by the chlorophenol hydroxylase from an Azotobacter sp. that is noted later. 

Distal fission Although substituted catechols generally undergo extradiol fission, this may produce toxic metabolites, and can be circumvented by regioselective 1,6-dioxygenation. This is rather uncommon but it has been observed in a number of degradations ... 

The second large group of ring-fission dioxygenases are used for the degradation of ortho-dihy-droxybenzoates including, 2,3-, 3,4-, and 4,5-dihydroxybenzoate. As for simple catechols, hssion may be either intradiol or extradiol, and the choice between them depends on the organism ... 

This comprises a heterogeneons gronp of enzymes that is used for the degradation of snbstrates including gentisate, salicylate, and l-hydroxynaphthalene-2-carboxylate by pathways that do not involve catechols ... 

Krooneman J, EBA Wieringa, ERB Moore, J Gerritse, RA Prins, JC Gottschal (1996) Isolation of Alcalig-enes sp. strain L6 at low oxygen concentrations and degradation of 3-chlorobenzoate via a pathway not involving (chloro)catechols. Appl Environ Microbiol 62 2427-2434. 

In a classical study, it was shown that during bacterial oxidation of benzene to catechol both atoms of oxygen came from 62 (Gibson et al. 1970). This initiated the appreciation of the role of dioxygenases in the degradation of aromatic xenobiotics, and many examples are given in Chapter 8, Parts 1 and 2. 

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