Bacterial degradation determines the environmental impact and efficacy of an herbicide or pesticide. Initially, most pesticides are highly effective and show minimal bacterial degradation; however, bacteria can rapidly evolve and gain the ability to metabolize potential nutrients in the environment. Despite a remarkable structural similarity, degradation of atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 by bacteria capable of melamine

Melamine

Melamine is an organic base and a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 66% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses....

 degradation was rare; however, since its introduction as a pesticide in the United States, bacteria capable of atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 degradation have evolved. Currently, Pseudomonas

Pseudomonas

Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...

sp. strain ADP seems to be the optimal bacterial strain for atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 degradations, which appears to be the sole nitrogen source for the bacteria.

Reaction

Atrazine Chlorohydrolase (AtzA) is an enzyme (E.C.3.8.1.8), which catalyzes the conversion of atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 to hydroxyatrazine. AtzA is an atrazine-dechlorinating enzyme with fairly restricted substrate specificity and plays a main role in the hydrolysis of atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 to hydroxyatrazine in soils and groundwater. Atrazine Hydroxyatrazine is a hydrolase (an enzyme that catalyzes the hydrolysis of a chemical bond ), which acts on halide bonds in C-halide compounds. In 1993, pseudomonas sp. strain ADP was shown to degrade atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 to cyanuric acid

Cyanuric acid

Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the formula 3. Like many industrially useful chemicals, this triazine has many synonyms. This white, odorless solid finds use as a precursor or a component of bleaches, disinfectants, and herbicides...

 via three steps, the first of which is a dechlorination.

Genetics

De Souza, Sadowsky and Wackett were able to determine the nucleotide and amino acid sequence in 1996. This enzyme is 98% identical in amino acid sequence, and subsequently in 3-D structure, to melamine deaminase but functionally different catalyzing the degradation of different substrates. The gene coding for the enzyme shows 99% similarity between bacteria. In fact there is only a 9-nucleotide difference, directly corresponding to the amino acid differences. The nucleotide differences are unlikely to cause a conformational change in the enzyme but rather site-specific alterations. This seems logical considering the remarkable similarity in the substrates and the relatively short period of evolution.

Specificity

AtzA was shown to displace fluoride as well as chlorine but not azido, cyano, methoxy, which are of similar size and electronegativity, or thiomethyl or amino groups. The inability of AtzA to perform deamination makes it unique within its superfamily, amidohydrolases. Furthermore, atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

 is not degraded by melamine deaminase and it does not inhibit melamine deaminase activity suggesting the active site is not specific for atrazine

Atrazine

Atrazine, 2-chloro-4--6--s-triazine, an organic compound consisting of an s-triazine-ring is a widely used herbicide. Its use is controversial due to widespread contamination in drinking water and its associations with birth defects and menstrual problems when consumed by humans at concentrations...

.