Novel enzymic hydrolytic dehalogenation of a chlorinated aromatic.
Microbial enzyme systems may be used in the biodegradation of persistent environmental pollutants. The three polypeptide components of one such system, the 4-chlorobenzoate dehalogenase system, have been isolated, and the chemical steps of the 4-hydroxybenzoate-forming reaction that they catalyze have been identified. The genes contained within a 4.5-kilobase Pseudomonas sp. strain CBS3 chromosomal DNA fragment that encode dehalogenase activity were selectively expressed in transformed Escherichia coli. Oligonucleotide sequencing revealed a stretch of homology between the 57-kilodalton (kD) polypeptide and several magnesium adenosine triphosphate (MgATP)-cleaving enzymes that allowed MgATP and coenzyme A (CoA) to be identified as the dehalogenase cosubstrate and cofactor, respectively. The dehalogenase activity arises from two components, a 4-chlorobenzoate:CoA ligase-dehalogenase (an alpha beta dimer of the 57- and 30-kD polypeptides) and a thioesterase (the 16-kD polypeptide).
Scholten
J D
JD
Department of Chemistry and Biochemistry, University of Maryland, College Park 20742.
Chang
K H
KH
Babbitt
P C
PC
Charest
H
H
Sylvestre
M
M
Dunaway-Mariano
D
D
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D002474:Cell-Free System; D002723:Chlorobenzoates / Q000378:metabolism*; D003001:Cloning, Molecular; D003065:Coenzyme A / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006867:Hydrolases / Q000235:genetics* / Q000378:metabolism; D006868:Hydrolysis; D008969:Molecular Sequence Data; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics*; D015183:Restriction Mapping
D002723:Chlorobenzoates; D004269:DNA, Bacterial; D000255:Adenosine Triphosphate; D006867:Hydrolases; C042846:4-chlorobenzoate dehalogenase; C040768:4-chlorobenzoic acid; D003065:Coenzyme A