Haloalkanes are serious environmental pollutants commonly employed as pesticides, herbicides, and chemical warfare agents. Although haloalkane production is performed mostly in the chemical industry, it also occurs naturally, mostly enzymatically (halide methyltransferases and haloperoxidases). Elimination of toxic haloalkanes is very important and using haloalkane dehalogenases is a promising and environmentally friendly way to achieve this.[53] Therefore, assays are needed for detecting dehalogenase activity either to find new enzymes or to generate laboratory-evolved variants. In this thesis, a new assay for dehalogenase activity was developed based on halide detection. In this assay halides, as dehalogenase products, are oxidized under mild conditions using the vanadium-dependent chloroperoxidase from Curvularia inaequalis, forming hypohalous acids that are detected using aminophenyl fluorescein.[53] This new halide oxidation assay is much more sensitive than previously known assays, with detection limits of 20 nM for bromide and 1 μM for chloride and iodide. Validation of the assay was done by comparison to a well-established GC-MS method in terms of determining the specific activities of two dehalogenases towards five common substrates (Figure 5). The HOX assay was modified for iodide-specific detection by using two other dyes, o-phenylenediamine (OPD) and 3,3′,5,5′-tetramethylbenzidine (TBM), instead of APF. Also, selective bromide detection in the presence of the ...