2O7V

Carboxylesterase AeCXE1 from Actinidia eriantha covalently inhibited by paraoxon

Summary for 2O7V

• Entry DOI: 10.2210/pdb2o7v/pdb
• Related: 2o7R
• Descriptor: CXE carboxylesterase, DIETHYL PHOSPHONATE (3 entities in total)
• Functional Keywords: carboxylesterase, actinidia eriantha, aecxe1, alpha/beta hydrolase, paraoxon, insecticide, hydrolase
• Biological source: Actinidia eriantha
• Total number of polymer chains: 1
• Total formula weight: 37589.86

Authors

Ileperuma, N.R.,Marshall, S.D.,Squire, C.J.,Baker, H.M.,Oakeshott, J.G.,Russell, R.J.,Plummer, K.M.,Newcomb, R.D.,Baker, E.N. (deposition date: 2006-12-11, release date: 2007-02-27, Last modification date: 2024-10-16)

Primary citation

Ileperuma, N.R.,Marshall, S.D.,Squire, C.J.,Baker, H.M.,Oakeshott, J.G.,Russell, R.J.,Plummer, K.M.,Newcomb, R.D.,Baker, E.N.
High-Resolution Crystal Structure of Plant Carboxylesterase AeCXE1, from Actinidia eriantha, and Its Complex with a High-Affinity Inhibitor Paraoxon.
Biochemistry, 46:1851-1859, 2007

PubMed Abstract: Carboxylesterases (CXEs) are widely distributed in plants, where they have been implicated in roles that include plant defense, plant development, and secondary metabolism. We have cloned, overexpressed, purified, and crystallized a carboxylesterase from the kiwifruit species Actinidia eriantha (AeCXE1). The structure of AeCXE1 was determined by X-ray crystallography at 1.4 A resolution. The crystal structure revealed that AeCXE1 is a member of the alpha/beta-hydrolase fold superfamily, most closely related structurally to the hormone-sensitive lipase subgroup. The active site of the enzyme, located in an 11 A deep hydrophobic gorge, contains the conserved catalytic triad residues Ser169, Asp276, and His306. Kinetic analysis using artificial ester substrates showed that the enzyme can hydrolyze a range of carboxylester substrates with acyl groups ranging from C2 to C16, with a preference for butyryl moieties. This preference was supported by the discovery of a three-carbon acyl adduct bound to the active site Ser169 in the native structure. AeCXE1 was also found to be inhibited by organophosphates, with paraoxon (IC50 = 1.1 muM) a more potent inhibitor than dimethylchlorophosphate (DMCP; IC50 = 9.2 muM). The structure of AeCXE1 with paraoxon bound was determined at 2.3 A resolution and revealed that the inhibitor binds covalently to the catalytic serine residue, with virtually no change in the structure of the enzyme. The structural information for AeCXE1 provides a basis for addressing the wider functional roles of carboxylesterases in plants.

PubMed: 17256879
DOI: 10.1021/bi062046w

Experimental method

X-RAY DIFFRACTION (2.3 Å)