Abstract
The N-isopropylammelide isopropylaminohydrolase from Pseudomonas sp. strain ADP, AtzC, provides the third hydrolytic step in the mineralization of s-triazine herbicides, such as atrazine. We obtained the X-ray crystal structure of AtzC at 1.84 Å with a weak inhibitor bound in the active site and then used a combination of in silico docking and site-directed mutagenesis to understand the interactions between AtzC and its substrate, isopropylammelide. The substitution of an active site histidine residue (His249) for an alanine abolished the enzyme’s catalytic activity. We propose a plausible catalytic mechanism, consistent with the biochemical and crystallographic data obtained that is similar to that found in carbonic anhydrase and other members of subtype III of the amidohydrolase family
Highlights
Since its introduction in the 1950s, atrazine has been used extensively for weed control in corn, sorghum and sugarcane, which has resulted in the detection of atrazine in ground and surface water at concentrations of up 4.6 μM
Atrazine is reportedly responsible for endocrine disruption in vertebrates, causing chemical feminization in frogs [1]
The availability of high concentrations of atrazine in the environment has promoted the evolution of new metabolic pathways in bacteria that allow the use of atrazine as a carbon and nitrogen source [2,3,4,5]
Summary
Since its introduction in the 1950s, atrazine has been used extensively for weed control in corn, sorghum and sugarcane, which has resulted in the detection of atrazine in ground and surface water at concentrations of up 4.6 μM. We present a 1.84 Å structure of AtzC with an inhibitor in the active site; this has guided substrate docking and mutagenesis experiments that have allowed us to propose a plausible reaction mechanism.
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