Limonene (4-isopropenyl-1-methyl-cyclohexene), a monocyclic monoterpene, is the most widespread terpene in the world and is formed by more than 300 plants. (+)-(4R)-limonene is its most widespread form (van der Werf et al., 1999). Limonene is the major constituent of citrus essential oils and is used as a raw material for the chemical synthesis of terpene resin adhesives and flavor materials, such as menthol and carvone.
So far, five different microbial biotransformation pathways for limonene have been proposed. In the middle branch, a soil Pseudomonassp. degradates limonene in the same way as Rhodococcus erythropolis DCL14, but its final product is 1-hydroxy-2-oxolimonene rather than 3-isopropenyl-6-oxoheptanoyl-CoA. The middle branch shows a pathway for (+)-(4R)-limonene; a similar pathway using many of the same enzymes is known for (-)-(4S)-limonene (van der Werf et al., 1999).
The following is a text-format limonene degradation pathway. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions.
Graphical Map(21k) Graphical Map(8k)
|--------------------------------------------| |-----------------------|
from the
alpha-Pinene ----------+------------------+----------------------+-----------------+
Pathway | | | |
| | | | |
V V V V V
Limonene Limonene (+)-(4R)-Limonene Limonene Limonene
Penicillium Pseudomonas sp. Rhodococcus Aspergillus Ps. gladioli
digitatum Aspergillus erythropolis DCL14 cellulosae Bacillus
Ps. gladioli cellulosae Pseudomonas sp. Hormonema sp. stearothermophilus
Arxula adeninivorans | | | Cladosporium sp.
Yarrowia lipolytica | | | P. digitatum
| | | | |
| limonene 7- | limonene 6- | limonene 1,2- | limonene 3- | limonene 8-
| monooxygenase | monooxygenase | monooxygenase | monooxygenase | hydratase
V V V V V
Perillyl alcohol Carveol (4R)-Limonene-1,2-epoxide Isopiperitenol alpha-Terpineol
| | | |
| perillyl | carveol | limonene-1,2- | isopiperitenol
| alcohol | dehydrogenase | epoxide hydrolase | dehydrogenase
| dehydrogenase | | |
V V V V
Perillyl aldehyde Carvone (1S,2S,4R)-Limonene-1,2-diol Isopiperitenone
| | |
| aldehyde | carvone | limonene-1,2-diol
| dehydrogenase | reductase | dehydrogenase
| | |
V V V
Perillic acid Dihydrocarvone (1S,4R)-1-Hydroxy-
| 2-oxolimonene
| |
| perillyl-CoA | 1-hydroxy-2-
| synthetase | oxolimonene
V | 1,2-monooxygenase
Perillyl-CoA V
| [(4R)-7-Hydroxy-4-isopropenyl-
| perillyl-CoA 7-methyl-2-oxo-oxepanone]
| hydratase |
| | spontaneous reaction
V |
2-Hydroxy-4- |
isopropenyl cyclohexane- V
1-carboxy-CoA (3R)-3-Isopropenyl-
| 6-oxoheptanoate
| 2-hydroxy-4-isopropenyl- |
| cyclohexane-1-carboxyl-CoA | 3-isopropenyl-
| dehydrogenase | 6-oxoheptanoyl-CoA
V | synthetase
4-Isopropenyl- |
2-ketocyclohexane- V
1-carboxy-CoA (3R)-3-Isopropenyl-
| 6-oxoheptanoyl-CoA
| 4-isopropenyl-2-ketocyclo-
| hexane-1-carboxy-CoA hydrolase
|
V
(3R)3-Isopropenyl-
(3R)pimelyl-CoA
Page Author(s): Shulan Tian and Meaghan Fitzgerald
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