maleoylacetic-acid and 2-chloromaleylacetate

The enzyme which cleaves the benzene ring of 6-chlorohydroxyquinol was purified to apparent homogeneity from an extract of 2,4,6-trichlorophenol-grown cells of Streptomyces rochei 303. Like the analogous enzyme from Azotobacter sp. strain GP1, it exhibited a highly restricted substrate specificity and was able to cleave only 6-chlorohydroxyquinol and hydroxyquinol and not catechol, chlorinated catechols, or pyrogallol. No extradiol-cleaving activity was observed. In contrast to 6-chlorohydroxyquinol 1,2-dioxygenase from Azotobacter sp. strain GP1, the S. rochei enzyme had a distinct preference for 6-chlorohydroxyquinol over hydroxyquinol (kcat/Km = 1.2 and 0.57 s-1.microM-1, respectively). The enzyme from S. rochei appears to be a dimer of two identical 31-kDa subunits. It is a colored protein and was found to contain 1 mol of iron per mol of enzyme. The NH2-terminal amino acid sequences of 6-chlorohydroxyquinol 1,2-dioxygenase from S. rochei 303 and from Azotobacter sp. strain GP1 showed a high degree of similarity.

Topics: Amino Acid Sequence; Azotobacter; Biodegradation, Environmental; Chlorophenols; Dioxygenases; Hydroquinones; Iron; Maleates; Metalloproteins; Molecular Sequence Data; Oxygenases; Protein Conformation; Sequence Analysis; Sequence Homology, Amino Acid; Streptomyces; Substrate Specificity

2,4-Dichlorophenoxyacetate (2,4-D) in Alcaligenes eutrophus JMP134 (pJP4) is degraded via 2-chloromaleylacetate as an intermediate. The latter compound was found to be reduced by NADH in a maleylacetate reductase catalyzed reaction. Maleylacetate and chloride were formed as products of 2-chloromaleylacetate reduction, the former being funneled into the 3-oxoadipate pathway by a second reductive step. There was no indication for an involvement of a pJP4-encoded enzyme in either the reduction or the dechlorination reaction.

Topics: 2,4-Dichlorophenoxyacetic Acid; Alcaligenes; Biodegradation, Environmental; Maleates; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors