Dichloromethane is a highly volatile solvent which finds application in a wide variety of industrial and commercial processes. It is used in paint removers, degreasing and cleaning fluids, and even as an extraction solvent in the decaffeination of coffee. Although dichloromethane is a potential carcinogen, the EPA Toxic Release Inventory reports that U.S. industrial discharges of dichloromethane amounted to 29,000 metric tons in 1994, down from 46,000 in 1990. The compound has an atmospheric half-life of several months, preventing it from reaching the stratosphere where it would be damaging to ozone. Both aerobic and anaerobic methylotrophic bacteria utilize dichloromethane as a carbon and energy source. A glutathione-dependent substitution which converts dichloromethane to inorganic chloride and formaldehyde (a central metabolite in methylotrophic growth) is the principal metabolic reaction in this degradation pathway.
Dichloromethane dehalogenase, the enzyme that catalyzes the first step of this pathway, also known to initiate the degradation of dibromomethane (CH2Br2), chlorofluoromethane (CH2ClF), bromochloromethane (CH2BrCl), and diiodomethane (CH2I2). Dibromomethane has been observed to occur naturally (Beissner et al., 1981).
The following is a text-format dichloromethane pathway map. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in Graphic (3k) format.
Dichloromethane Methylophilus sp. DM11 Pseudomonas sp. Hyphomicrobium sp. DM2 Methylobacterium sp. DM4 | | | | dichloromethane dehalogenase | | v Formaldehyde | | | | | | v to the C1 Metabolic Cycle
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