2011 Volume 28 Pages 58-64
Enzymes that catalyze the degradation of organohalogen compounds are useful in environmental technology and chemical industry. Burkholderia sp. WS is a Gram-negative bacterium that can utilize an aliphatic unsaturated organohalogen compound, 2-chloroacrylate (2-CAA), as its sole carbon source. The production of 2 proteins, CAA43 and CAA67_WS, is induced when the bacterium is grown in 2-CAA medium. CAA43 catalyzes the conversion of 2-CAA into (S)-2-chloropropionate, whereas the function of CAA67_WS remains unknown. Recently, a homolog of CAA67_WS from Pseudomonas sp. YL (CAA67_YL), subsequently named 2-haloacrylate hydratase, was shown to catalyze the FADH2-dependent hydration of 2-CAA to produce pyruvate. Our results suggest that CAA67_WS has a similar activity. Gene-disruption studies of CAA43 and CAA67_WS indicated that CAA67_WS is physiologically more important in the assimilation of 2-CAA in Burkholderia sp. WS. The enzyme CAA67_WS was purified from Burkholderia sp. WS and characterized. The UV-visible spectrum of the protein indicated the presence of bound flavin. CAA67_WS released chloride ions from 2-CAA in the presence of FAD and reducing agents such as NAD(P)H. CAA67_WS is similar to CAA67_YL in these respects. However, while the reduced form of flavin mononucleotide (FMN) served as a cofactor for CAA67_WS, it did not for CAA67_YL. CAA67_YL is a bifunctional enzyme that catalyzes the hydration of 2-CAA and the reduction of FAD by using NADH; CAA67_WS did not catalyze the reduction of FAD. Thus, comparative studies of these 2 proteins can provide valuable information on the structure-function relationship of these proteins.
Abbreviations: 2-CAA, 2-chloroacrylic acid (S)-2-CPA, (S)-2-chloropropionic acid ESI-MS, electrospray ionization mass spectrometry
