The binding of substrate analogs to phosphotriesterase.
Phosphotriesterase (PTE) from Pseudomonas diminuta catalyzes the detoxification of organophosphates such as the widely utilized insecticide paraoxon and the chemical warfare agent sarin. The three-dimensional structure of the enzyme is known from high resolution x-ray crystallographic analyses. Each subunit of the homodimer folds into a so-called TIM barrel, with eight strands of parallel beta-sheet. The two zinc ions required for activity are positioned at the C-terminal portion of the beta-barrel. Here, we describe the three-dimensional structure of PTE complexed with the inhibitor diisopropyl methyl phosphonate, which serves as a mimic for sarin. Additionally, the structure of the enzyme complexed with triethyl phosphate is also presented. In the case of the PTE-diisopropyl methyl phosphonate complex, the phosphoryl oxygen of the inhibitor coordinates to the more solvent-exposed zinc ion (2.5 A), thereby lending support to the presumed catalytic mechanism involving metal coordination of the substrate. In the PTE-triethyl phosphate complex, the phosphoryl oxygen of the inhibitor is positioned at 3.4 A from the more solvent-exposed zinc ion. The two structures described in this report provide additional molecular understanding for the ability of this remarkable enzyme to hydrolyze such a wide range of organophosphorus substrates.
Benning
M M
MM
Department of Biochemistry, University of Wisconsin, Madison, USA.
Hong
S B
SB
Raushel
F M
FM
Holden
H M
HM
D043303:Aryldialkylphosphatase; D002619:Chemical Warfare Agents; D002800:Cholinesterase Inhibitors; D018360:Crystallography, X-Ray; D004950:Esterases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D018716:Molecular Mimicry; D010755:Organophosphates / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry* / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology; D012524:Sarin; D015032:Zinc / Q000737:chemistry
D002619:Chemical Warfare Agents; D002800:Cholinesterase Inhibitors; D010755:Organophosphates; D009943:Organophosphorus Compounds; C023477:diisopropyl methylphosphonate; D012524:Sarin; D004950:Esterases; D043303:Aryldialkylphosphatase; D015032:Zinc; C009549:triethyl phosphate