Molecular Genetics of the Gentisate Pathway of Aromatic Hydrocarbon Degradation in Pseudomonas alcaligenes P25X
(Collaborative project with the National University of Singapore and the Institute of Environmental Science and Engineering, Nanyang Technological University, Singapore)
Pseudomonas alcaligenes NCIB 9867 (strain P25X) is a soil bacterium that is capable of degrading xylenols and cresols via the gentisate pathway of aromatic hydrocarbon catabolism. Biochemical analysis of several P25X-derived catabolic mutants revealed the existence of isofunctional enzymes of the degradative pathway - one set of enzymes being constitutively expressed, and the other set, strictly inducible by aromatic substrates such as 3-hydroxybenzoate. The key enzyme in this pathway is gentisate 1,2-dioxygenase (GDO; EC 1.13.11.4) that catalyzes the cleavage of the gentisate (2,5-dihydroxybenzoate) aromatic ring between the carboxyl and vicinal hydroxyl groups yielding maleylpyruvate as the ring fission product.
We have cloned one copy of the GDO gene, designated xlnE, and found that it was part of a six gene operon, xlnEFGHID. We are interested to elucidate the regulation of expression of these genes in P25X. The function of the other genes in the operon would also be investigated. We would also carry out proteome mapping of P25X cells in response to aromatic compounds, which would give us an idea of the proteins that are expressed by the bacterium in the presence of aromatic hydrocarbons in its environment.
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The gentisate pathway for the degradation of 2,5-xylenol
in Pseudomonas alcaligenes NCIB 9867 (strain P25X) |
Principal Investigators at MUST
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