3-Hydroxylaminophenol Mutase from Ralstonia eutropha JMP134 Catalyzes a Bamberger Rearrangement

Abstract

3-Hydroxylaminophenol mutase from Ralstonia eutrophaJMP134 is involved in the degradative pathway of 3-nitrophenol, in which it catalyzes the conversion of 3-hydroxylaminophenol to aminohydroquinone. To show that the reaction was really catalyzed by a single enzyme without the release of intermediates, the corresponding protein was purified to apparent homogeneity from an extract of cells grown on 3-nitrophenol as the nitrogen source and succinate as the carbon and energy source. 3-Hydroxylaminophenol mutase appears to be a relatively hydrophobic but soluble and colorless protein consisting of a single 62-kDa polypeptide. The pI was determined to be at pH 4.5. In a database search, the NH2-terminal amino acid sequence of the undigested protein and of two internal sequences of 3-hydroxylaminophenol mutase were found to be most similar to those of glutamine synthetases from different species. Hydroxylaminobenzene, 4-hydroxylaminotoluene, and 2-chloro-5-hydroxylaminophenol, but not 4-hydroxylaminobenzoate, can also serve as substrates for the enzyme. The enzyme requires no oxygen or added cofactors for its reaction, which suggests an enzymatic mechanism analogous to the acid-catalyzed Bamberger rearrangement.

Metabolic reconstruction of aromatic compounds degradation from the genome of the amazing pollutant-degrading bacteriumCupriavidus necatorJMP134

“…Three nitrophenols support the growth of C. necator JMP134: 2,6-dinitrophenol (Ecker et al, 1992), 3-nitrophenol (Schenzle et al, 1997) and 2-chloro-5-nitrophenol (Schenzle et al, 1999a). The initial degradation pathway for 3-nitrophenol consists of the transformation into 3-hydroxylaminophenol and then into aminohydroquinone; these are catalyzed by a 3-nitrophenol nitroreductase (MnpA) and a 3-hydroxylaminophenol mutase (Fig.…”

“…The 3-hydroxylaminophenol mutase was identified as a glutamine syntethase (Table 5) (Schenzle et al, 1999b). The initial degradation of 2-chloro-5-nitrophenol is analogous to that of 3-nitrophenol, and results in the formation of 2-amino-5-chlorohydroquinone (Schenzle et al, 1999a). The removal of the chlorine group in the latter intermediate is reductively mediated and produces aminohydroquinone, a common intermediate.…”

Branching ofo-nitrobenzoate degradation pathway inArthrobacter protophormiaeRKJ100: identification of new intermediates

“…The presence of AA and HAA in the degradation pathway of 20 mM ONB led us to hypothesize that 2‐HABA is a substrate for two different enzymes, a reductase and a mutase. The reductase catalyzes the conversion of HABA to AA by reducing the hydroxylamino group to an amino group while the mutase converts HABA to HAA through a Bamberger‐like rearrangement [32]. Results of enzyme assays of both enzymes acting at the branching point support this hypothesis.…”

Biodegradation of 4-nitrobenzoate, 4-aminobenzoate and their mixtures: new strains, unusual metabolites and insights into pathway regulation

“…These authors found two genes encoding hydroxylaminobenzene mutase in nitrobenzene-degrading Pseudomonas pseudoalcaligenes JS45. Schenzle et al [39] described amino acid sequences of the NH 2 -terminus and of two internal sequences of a 3-hydroxylaminophenol mutase from Ralstonia eutropha JMP134. These sequences have no homologies to the deduced amino acid sequence of the two hydroxylaminobenzene mutases in P. pseudoalcaligenes JS45 [38].…”