Camphor exists in two enantiomers, but the (+)-isomer is more widely distributed. The bicyclic monoterpene ketone (+)-camphor is one of the major components in the leaves of common sage. Camphor and other terpenoid compounds do not accumulate in the environment due to their ready metabolism by many soil bacteria. The best studied reactions of this type are the early steps of the (+)-camphor degradation pathway which require the cytochrome P-450cam hydroxylase operon (camDCAB) on the CAM plasmid of Pseudomonas putida ATCC 17453. Reactions for the partial oxidation of (+)-camphor have been shown to proceed by an initial hydroxylation at carbon 5, followed by dehydrogenation to form 2,5-diketocamphane. Subsequent ring oxidation by a 1,2-monooxygenase, results in the formation of a 5-oxo-1,2-campholide (Jones et al., 1993). This 5-oxo-1,2-campholide may be unstable and undergo spontaneous cleavage to form 2-oxo-delta3-4,5,5-trimethylcyclopentenylacetate. The synthesis of 2-oxo-delta3-4,5,5-trimethylcyclopentenylacetyl-CoA was detected when an extract of (+)-camphor-grown Pseudomonas putida was incubated with 2-oxo-delta3-4,5,5-trimethylcyclopentenylacetate, CoA, ATP, and CoA ester synthetase (Ougham et al., 1983). The involvement of 2-oxo-delta3-4,5,5-trimethyl-cyclopentenylacetyl-CoA 1,2-monooxygenase was not experimentally established but it is suggested by the accumulation of the delta-lactone of 5-hydroxy-3,4,4-trimethyl-delta2-pimelyate from 2-oxo-delta3 -4,5,5-trimethylcyclopentenylacetate. The further metabolism of the ring cleavage remains to be elucidated.
The following is a text-format (+)-camphor degradation pathway map. An organism which can initiate the pathway is given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in graphic (14k) format.
(+)-Camphor
Pseudomonas putida ATCC 17453
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| camphor 5-monooxygenase
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v
5-exo-Hydroxycamphor
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| 5-exo-hydroxycamphor
| dehydrogenase
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v
2,5-Diketocamphane
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| 2,5-diketocamphane
| 1,2-monooxygenase
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v
[5-Oxo-1,2-campholide]
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| spontaneous
| reaction
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v
2-Oxo-delta3-4,5,5-trimethyl-
cyclopentenylacetate
|
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| 2-oxo-delta3-4,5,5-trimethyl-
| cyclopentenylacetyl-CoA synthetase
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|
v
2-Oxo-delta3-4,5,5-trimethyl-
cyclopentenylacetyl-CoA
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|
| 2-oxo-delta3-4,5,5-trimethyl-
| cyclopentenylacetyl-CoA
| 1,2-monooxygenase
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v
[5-Hydroxy-3,4,4-trimethyl-
delta2-pimelyl-CoA-delta-lactone]
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| spontaneous
| reaction
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v
delta2,5-3,4,4-Tri-
methylpimelyl-CoA
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v A
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v
Isobutyryl-CoA + Acetyl-CoA
| |
| |
| |
| |
v v
Intermediary Intermediary
Metabolism Metabolism
(KEGG) (KEGG)
Page Author(s): Jian Ma and Dong Jun Oh
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