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J. Bacteriol., 06 1997, 3549-3554, Vol 179, No. 11
B Rosche, B Tshisuaka, B Hauer, F Lingens and S Fetzner
2-Oxo-1,2-dihydroquinoline 8-monooxygenase, an enzyme involved in quinoline
degradation by Pseudomonas putida 86, had been identified as a class IB
two-component nonheme iron oxygenase based on its biochemical and
biophysical properties (B. Rosche, B. Tshisuaka, S. Fetzner, and F.
Lingens, J. Biol. Chem. 270:17836-17842, 1995). The genes oxoR and oxoO,
encoding the reductase and the oxygenase components of the enzyme, were
sequenced and analyzed. oxoR was localized approximately 15 kb downstream
of oxoO. Expression of both genes was detected in a recombinant Pseudomonas
strain. In the deduced amino acid sequence of the NADH:(acceptor) reductase
component (OxoR, 342 amino acids), putative binding sites for a
chloroplast-type [2Fe- 2S] center, for flavin adenine dinucleotide, and for
NAD were identified. The arrangement of these cofactor binding sites is
conserved in all known class IB reductases. A dendrogram of reductases
confirmed the similarity of OxoR to other class IB reductases. The
oxygenase component (OxoO, 446 amino acids) harbors the conserved amino
acid motifs proposed to bind the Rieske-type [2Fe-2S] cluster and the
mononuclear iron. In contrast to known class IB oxygenase components, which
are composed of differing subunits, OxoO is a homomultimer, which is
typical for class IA oxygenases. Sequence comparison of oxygenases indeed
revealed that OxoO is more related to class IA than to class IB oxygenases.
Thus, 2-oxo-1,2-dihydroquinoline 8-monooxygenase consists of a class
IB-like reductase and a class IA-like oxygenase. These results support the
hypothesis that multicomponent enzymes may be composed of modular elements
having different phylogenetic origins.
Copyright © 1997, American Society for Microbiology
2-oxo-1,2-dihydroquinoline 8-monooxygenase: phylogenetic relationship to other multicomponent nonheme iron oxygenases
Universitat Hohenheim, Institut fur Mikrobiologie, Stuttgart, Germany.
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