ABSTRACT
References .......................................................................................................................... 459
The first descriptions of dehalogenases date back to the 1960s. Davies and Evans [1] and
Goldman [2] described enzymes that dehalogenate fluoroacetate, and Castro and Bartnicki [3]
studied an enzyme that releases bromide from 2,3-dibromo-1-propanol. Dehalogenases were
initially classified on the basis of their substrate range. However, genetic analysis has revealed
that dehalogenases acting on similar substrates (e.g., fluoroacetate and chloroacetate) may
belong to unrelated protein families, whereas dehalogenases that act on rather different
substrates (e.g., fluoroacetate and 1,2-dibromoethane) may belong to the same phylogenetic
superfamily. Fluoroacetate, 1,2-dichloroethane, 1,3-dichloropropene, and tetrachlorocyclo-
hexadiene are dehalogenated by dehalogenases that have low sequence similarity, but all four
belong to the a/b-hydrolase fold family. Most 2-chlorocarboxylic acid dehalogenases that
442 Biocatalysis in the Pharmaceutical and Biotechnology Industries
have been studi ed belong to the HAD superf amily of de halogenas es-phosp hatases (Table
16.1, L -DEX, DhlB) [4], but there are also haloaci d deh alogenas es such as the DL -2-haloaci d
deh alogenas e from Pseudom onas sp. 113 [5], that are not related to the HAD superf amily,
and form a separat e group of enzymes , some of whic h are specif ic for D-chlor opropionic
acid. The phy logenetic class ificatio n, as used in Table 16.1, is now replacing the old
substr ate-ba sed classif ication in most studies, and the major ity of haloacid dehalogenas es
can be group ed into two fami lies [4].
