Atrazine is a broad-leaf, pre-emergence herbicide. Eighty million pounds are applied to soils annually in the United States, more than any other herbicide. Atrazine is the leading member of a class of triazine ring-containing herbicides that includes simazine and terbuthylazine. The Triazine Metapathway Map contains additional information on triazine metabolism. A number of different bacteria have been identified that are capable of metabolizing atrazine to ammonia and carbon dioxide.
Atrazine biodegradation has been found to occur via several different pathways that funnel into cyanuric acid metabolism. A gene region from Pseudomonas sp. strain ADP encoding atrazine degradation enzymes has been cloned and characterized. The initial hydrolytic dechlorination of atrazine to hydroxyatrazine (de Souza et al., 1995) is an animated reaction. Two enzymes belonging to the amidohydrolase protein family catalyze the sequential removal of ethylamine and isopropylamine (Boundy-Mills et al., 1997 and Sadowsky et al., 1998). Degradation by Rhodococcus sp. strain N186/21 is initiated by oxidative removal of either the ethyl or isopropyl group (Nagy et al., 1995). Deethylatrazine undergoes a second oxidative removal of the isopropyl group. Hydrolytic removal of s-triazine ring substituents from deisopropylatrazine and deisopropyldeethylatrazine yields cyanuric acid.
The following is a text-format atrazine degradation 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 (6k) | Graphical Map (13k)
Atrazine Atrazine Atrazine
Pseudomonas sp. ADP Rhodococcus spp. Rhodococcus spp.
Ralstonia sp. M91-3 NI86/21, TE1 NI86/21, TE1
Clavibacter sp. Pseudomonas spp. Nocardia sp.
Agrobacterium sp. J14a 192, 194 Streptomyces sp. PS1/5
Alcaligenes sp. SG1 Streptomyces sp. PS1/5 |
Arthrobacter aurescens TC1 | |
| atrazine | atrazine |
| monooxygenase | monooxygenase |
atrazine | | |
chloro- | | |
hydrolase | v v
| Deisopropylatrazine Deethylatrazine
| Rhodococcus |
| corallinus |
v NRRLB-15444R |
Hydroxyatrazine | |
| | |
| | |
hydroxy- | s-triazine | deethyl- |
atrazine | hydrolase | atrazine |
ethylamino- | | mono- |
hydrolase | | oxygenase |
| | |
| | |
v v v
N-Isopropylammelide Deisopropyl- Deisopropyl-
| hydroxyatrazine deethylatrazine
| | Pseudomonas sp. NRRLB-12227
| | |
N-isopropyl- | deisopropyl- | |
ammelide | hydroxy- | |
isopropyl- | atrazine | s-triazine |
amino- | amino- | hydrolase |
hydrolase | hydrolase | |
| | |
| | |
| | |
| v v
| 2,4-Dihydroxy- 2-Chloro-4-
| 6-(N'-ethyl)- hydroxy-6-amino-
| amino-1,3,5-triazine 1,3,5-triazine
| Pseudomonas sp. NRRLB-12228 |
| | |
| | | hydroxychloro-
| | | atrazine
| 2,4-dihydroxy- | | ethylamino-
| 6-(N'-ethyl)- | | hydrolase
| amino-1,3,5- | |
| triazine | |
| aminohydrolase | 2,4-Dihydroxy-6-
| | amino-1,3,5-triazine
| | |
| | |
+------------+-----------+ | N-isopropyl-
| | ammelide
| | isopropylamino-
| | hydrolase
v |
Cyanuric acid <---------------------------+
|
|
|
|
|
v
to the
Cyanuric acid Pathway
Page Author(s): Yuemo Zeng, Colin L. Sweeney, Stephen Stephens, Prasad Kotharu and Michael Turnbull
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