L. Garbe, M. Moreno-Horn, D. Rewicki
Jun 7, 2004
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0
Influential Citations
4
Citations
Journal
ChemBioChem
Abstract
Bis(chloropropyl)ethers are undesirable by-products of the industrial production of propylenoxide and epichlorohydrine by the two-step chlorohydrine process. Such by-products have been released into the environment. They are considered an important class of environmental pollutants due to their persistence and toxicity. Compounds containing an ether bond are poorly biodegradable because the ether bridge is very stable. In addition, metabolites resulting from ether transformation may be toxic for organisms or the organisms may lack the necessary enzymes for further degradation. The aerobic biodegradation of bis(1-chloro-2-propyl)ether (1, DDE) by the Rhodococcus species strain DTB occurs by scission of the ether bridge resulting in the formation of chloroacetone (4), 1-chloropropan-2-ol (5) and the transient formation of a so far unknown metabolite. The possible involvement of a flavin-containing monooxygenase and the formation of chloroacetone and 1-chloropropan-2-ol may indicate that scission of the ether bond is initiated by hydroxylation of DDE at C-2, which results in a hemiketal structure 3 that is unstable in aqueous solution and predisposed to spontaneous scission. It has been suggested by several groups that scission of ether compounds under aerobic conditions occurs via the formation of hemiacetal intermediates, the formation of which was proposed exclusively on the identification of the cleavage products, for example, the resulting alcohols and aldehydes. It was suggested that the conversion of the gasoline compound methyl tert-butyl ether into tert-butyl alcohol and formaldehyde occurs by hydroxylation, which leads to the formation of hydroxymethyl tert-butyl ether. It was proposed that the scission of diethyl ether by the Graphium sp. strain ATCC 58400 occurs by a cytochrome P450-mediated hydroxylation of the carbon atom adjacent to the ether bridge, which leads to the formation of a hemiacetal. However, ether-cleaving methane monooxygenase (MMO) is known to catalyze hydroxylation but also desaturation reactions, which after hydration will also result in a hemiacetal structure with ether as substrate. In contrast to hydroxylation of the carbon atom adjacent to the ether bridge, hemiacetal structures can also be achieved by hydroxyl shifts or by the addition of water to vinyl ethers. 8] For example, such a vinyl ether mechanism was proposed for isochorismate pyruvate hydrolase (EC 3.3.2.1), which catalyzes the conversion of isochorismic acid to 2,3-dihydro2,3-dihydroxybenzoic acid and pyruvate, while a hydroxyl shift route is operative with glycol monoethyl ether. In order to get further hints for the mechanism of ether scission with DDE, the unknown metabolite was isolated and its structure was determined by MS and NMR spectroscopy. Here we report the transient formation and characterization of an as yet unknown dichloro vinyl ether (DVE) 2 by the Rhodococcus sp. strain DTB during growth on DDE 1 (Figure 1).