Similarities between the antABC -Encoded Anthranilate Dioxygenase and the benABC -Encoded Benzoate Dioxygenase of Acinetobacter sp. Strain ADP1

Abstract

Acinetobacter sp. strain ADP1 can use benzoate or anthranilate as a sole carbon source. These structurally similar compounds are independently converted to catechol, allowing further degradation to proceed via the β-ketoadipate pathway. In this study, the first step in anthranilate catabolism was characterized. A mutant unable to grow on anthranilate, ACN26, was selected. The sequence of a wild-type DNA fragment that restored growth revealed theantABC genes, encoding 54-, 19-, and 39-kDa proteins, respectively. The deduced AntABC sequences were homologous to those of class IB multicomponent aromatic ring-dihydroxylating enzymes, including the dioxygenase that initiates benzoate catabolism. Expression of antABC in Escherichia coli, a bacterium that normally does not degrade anthranilate, enabled the conversion of anthranilate to catechol. Unlike benzoate dioxygenase (BenABC), anthranilate dioxygenase (AntABC) catalyzed catechol formation without requiring a dehydrogenase. In Acinetobacter mutants,benC substituted for antC during growth on anthranilate, suggesting relatively broad substrate specificity of the BenC reductase, which transfers electrons from NADH to the terminal oxygenase. In contrast, the benAB genes did not substitute for antAB. An antA point mutation in ACN26 prevented anthranilate degradation, and this mutation was independent of a mucK mutation in the same strain that prevented exogenous muconate degradation. Anthranilate induced expression of antA, although no associated transcriptional regulators were identified. Disruption of three open reading frames in the immediate vicinity ofantABC did not prevent the use of anthranilate as a sole carbon source. TheantABC genes were mapped on the ADP1 chromosome and were not linked to the two known supraoperonic gene clusters involved in aromatic compound degradation.

Comparative genome analysis of Pseudomonas knackmussii B13, the first bacterium known to degrade chloroaromatic compounds

“…Downstream of those and in opposite direction (antCBA, PKB_2111-2113) are three genes for anthranilate dioxygenase, which may lead to production of catechol from anthranilate (Bundy et al, 1998). Fragments of another multicomponent anthranilate dioxygenase (PKB3281_3282) are also found on ICEclc.…”

Evolution of the soluble diiron monooxygenases

“…Abbreviations, accession numbers, and references for other sequences are as follows: AntC, anthranilate dioxygenase of Acinetobacter sp. strain ADP1, AF071556 [154]; BenC, benzoate 1,2-dioxygenase of Acinetobacter sp. strain ADP1, M76990, M62649 [152]; CarAd, carbazole 2,3-dioxygenase of P. stutzeri OM1, AB001723 [155]; CbdC, 2-halobenzoate 1,2-dioxygenase of B. cepacia 2CBS, X79076 [156]; DntAa, 2,4-dinitrotoluene dioxygenase of Burkholderia sp.…”

Pathway Analysis of Acinetobacter baylyi: A Combined Bioinformatic and Genomics Approach

“…Expression of antABC in E. coli, a bacterium that normally does not degrade anthranilate, enabled the conversion of anthranilate to catechol (52). However, catechol formation from benzoate requires a second enzymatic step that is catalyzed by the ben-D encoded dehydroxygenase (53).…”

“…Further, conversion of benzoate to catechol requires benzoate dioxgenase encoding benABC genes. Also, the ant genes, shown to encode anthranilate dioxygenase, were homologous in sequence to the benzoate dioxygenase encoding benABC genes (52). The benM gene encodes a transcriptional activator of benC expression (54).…”

“…The benM gene encodes a transcriptional activator of benC expression (54). Moreover, it is likely that in the absence of antC, benC was required for growth on anthranilate, because the benC reductase can substitute for antC in anthranilate oxidation (52).…”