Biodegradation of both isomers (cis- and trans-) of 3-chloroacrylic acid has been experimentally demonstrated and reported (Hartmans et al., 1991; van Hylckama Vlieg and Janssen, 1991). Burkholderia cepacia strain CAA2, a coryneform bacterium, is able to utilize either isomer as a sole source of carbon and energy. However, two distinct enzymes are employed by the organism in the degradation process (one corresponding to each isomer), rather than a single enzyme with a relaxed substrate specificity. The two articles cited above are in conflict regarding the classification of these enzymes: Hartmans et al. 1991 proposes that the inchoative steps are a hydration and a subsequent spontaneous decomposition and thus concludes that the enzyme involved is a hydratase, whereas van Hylckama Vlieg and Janssen 1991 points to dehalogenation as the primary function of the enzyme and thus classifies it as a dehalogenase. Poelarends et al. (1998) supports the latter proposition by showing that a trans-specific dehalogenase that is constitutively expressed and an inducible cis-specific dehalogenase are involved in the dechlorination of the 3-chloroacrylic acid isomers by Pseudomonas cichorii 170. We have used dehalogenase for both organisms. The last enzyme in this pathway, malonate semialdehyde decarboxylase, is the first identified decarboxylase in the tautomerase superfamily (Poelarends et al., 2003).
The following is a text-format 3-Chloroacrylic acid 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 (7k) format.
from the from the 1,3-Dichloropropene 1,3-Dichloropropene Pathway Pathway | | | | | | v v cis-3-Chloroacrylic acid trans-3-Chloroacrylic acid Burkholderia cepacia CAA2 Burkholderia cepacia CAA2 Pseudomonas cichorii 170 Pseudomonas cichorii 170 | | | | | cis-chloroacrylic | trans-chloroacrylic | acid dehalogenase | acid dehalogenase | | | | +--------->Malonate semialdehyde<-------+ | | | malonate semialdehyde decarboxylase | | v Acetaldehyde | | | | | v Intermediary Metabolism (KEGG)
Page Author(s): Melissa A. McCornack, Ryan McLeish and Jenny Kang
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