When styrene is heated, exposed to light, or in the presence of a peroxide catalyst, it undergoes polymerization to form polystyrene, a versatile material used in the manufacture of plastics, synthetic rubber, thermal insulation, and packaging. Although polystyrene has many beneficial commercial applications, the styrene monomer is a classified mutagen and a suspected carcinogen. It is highly toxic to aquatic life, although its half-life is less than two days in water. There are several microorganisms that are capable of initiating styrene biodegradation, and metabolism proceeds via one of two known pathways; the principal reaction may either be an ethylene side-chain monooxygenation (Cox et al., 1996) or a 2,3-dioxygenation (Warhurst et al., 1994).
The following is a text-format styrene pathway map. 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 (17k) Graphical Map (13k)
Styrene Styrene
Exophiala jeanselmei Rhodococcus rhodochrous NCIMB 13259
Pseudomonas putida CA-3 |
| |
| |
| styrene | styrene
| monooxygenase | dioxygenase
| |
v v
Styrene oxide Styrene cis-glycol
| |
| |
| styrene oxide | cis-glycol
| isomerase | dehydrogenase
| |
v v
Phenylacetaldehyde 3-Vinylcatechol
| |
| |
| phenylacetaldehyde | catechol
| dehydrogenase | 2,3-dioxygenase
| |
v from the v
Phenylacetate <--Z-Phenylac- 2-Hydroxy-6-oxo-octa-
| -etaldoxime trienoate
| Pathway /\
| / \
| phenylacetate / \ 2-hydroxymuconate
| hydroxylase / \ semialdehyde hydrolase
| / \
v v v
2-Hydroxyphenylacetate Acrylate + 2-Hydroxypenta-
| | 2,4-dienoate
| | |
| 2-hydroxyphenyl- v |
| acetate to the | 2-hydroxypenta-2,4-dienoate
| hydroxylase Acrylonitrile | hydratase
| Pathway |
v v
Homogentisate 4-Hydroxy-2-oxovalerate
| /\
| / \
| homogentisate / \ 4-hydroxy-2-oxovalerate
| 1,2-dioxygenase / \ aldolase
| / \
v v v
4-Maleylacetoacetate Acetaldehyde + Pyruvate
| | |
| maleylacetoacetate | |
| isomerase | |
| | |
v v v
Fumarylacetoacetate Intermediary Intermediary
/\ Metabolism Metabolism
/ \ (KEGG) (KEGG)
/ \ fumarylacetoacetase
/ \
/ \
v v
Fumarate + Acetoacetate
| |
| |
| |
| |
| |
v v
Intermediary Intermediary
Metabolism Metabolism
(KEGG) (KEGG)
Page Author(s): Dean Kraus, Andrea Marconi, Kenneth E. Lind and Ryan McLeish
April 25, 2008 Contact Us
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