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3-Hydroxylaminophenol mutase from Ralstonia eutropha JMP134 catalyzes a Bamberger rearrangement
A Schenzle1, H Lenke, J C Spain
1Fraunhofer Institut für Grenzflächen- und Bioverfahrenstechnik, D-70569 Stuttgart, Germany.
Journal of Bacteriology
|February 27, 1999
Summary
3-Hydroxylaminophenol mutase from Ralstonia eutropha JMP134 catalyzes a key step in 3-nitrophenol degradation. This enzyme converts 3-hydroxylaminophenol to aminohydroquinone without intermediates, showing a novel enzymatic mechanism.
Area of Science:
- Biochemistry
- Microbial Metabolism
Background:
- 3-Nitrophenol is a toxic environmental pollutant.
- Ralstonia eutropha JMP134 possesses a degradative pathway for 3-nitrophenol.
- 3-Hydroxylaminophenol mutase is a key enzyme in this pathway.
Purpose of the Study:
- To purify and characterize 3-hydroxylaminophenol mutase from Ralstonia eutropha JMP134.
- To elucidate the catalytic mechanism and substrate specificity of the enzyme.
- To investigate its role in 3-nitrophenol biodegradation.
Main Methods:
- Purification of 3-hydroxylaminophenol mutase to apparent homogeneity.
- Determination of protein properties (molecular weight, pI, solubility).
- NH2-terminal and internal protein sequencing for database comparison.
- Enzyme activity assays with various hydroxylaminobenzene derivatives.
Main Results:
- Purified 3-hydroxylaminophenol mutase is a 62-kDa, single polypeptide, hydrophobic, soluble, colorless protein with a pI of 4.5.
- Amino acid sequences show similarity to glutamine synthetases.
- The enzyme accepts hydroxylaminobenzene, 4-hydroxylaminotoluene, and 2-chloro-5-hydroxylaminophenol as substrates.
- No oxygen or cofactors are required, suggesting an acid-catalyzed mechanism.
Conclusions:
- 3-Hydroxylaminophenol mutase is a novel enzyme catalyzing the conversion of 3-hydroxylaminophenol to aminohydroquinone.
- Its mechanism may be analogous to the Bamberger rearrangement.
- The enzyme plays a crucial role in the microbial degradation of 3-nitrophenol.