Hydrolytic activity of PTE<i>_Ar</i>.

<p>A) Schematic showing the PTE<i>_Ar</i>-mediated hydrolysis of malathion. B) Structure of the OP insecticides demeton, chlorpyrifos, parathion and diazinon.</p

Brønsted plot of leaving group pKa values <i>vs</i> log(<i>k</i>_cat/<i>K</i>_M) for a range of substates.

<p>The p<i>K</i>_a values of the leaving groups 2,6-difluoro-4-nitrophenol; quinoxalin-2-ol; 2-fluoro-4-nitrophenol; 2-isopropyl-6-methylpyrimidin-4-ol; 3-fluoro-4-nitrophenol; 4-nitrophenol; 4-hydroxybenzaldehyde; 2,2-dichloroethylenol; 4-hydroxybenzonitrile; 1-(4-hydroxyphenol)ethanone; methyl 4-hydroxybenzoate; 4-hydroxybezamide; 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one; 2-(ethylthio)ethanethiol; 2-(diethylamino)ethanethiol; 2-(diisopropylamino)ethanethiol; and 4-(methoxymethyl)phenol plotted (left to right) against their log(<i>k</i>_cat/<i>K</i>_M) values. p<i>K</i>_a values were as published elsewhere <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Caldwell1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Jackson4" target="_blank">[17]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Jackson7" target="_blank">[20]</a> or as calculated using the SPARC online p<i>K</i>_a calculator (<a href="http://ibmlc2.chem.uga.edu/sparc/" target="_blank">http://ibmlc2.chem.uga.edu/sparc/</a>) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Hilal1" target="_blank">[38]</a>. The biphasic dependence of the enzyme on p<i>K</i>_a as described elsewhere <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Caldwell1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094177#pone.0094177-Jackson7" target="_blank">[20]</a> is shown: the curve flattens below a p<i>K</i>_a of ∼8.0 and there is a linear dependence on p<i>K</i>_a at values below <i>ca</i>. 8.0.</p

Kinetic parameters of purified PTE<i>_Ar</i> and most active variant against malathion for a range of OP insecticides.

<p>Standard deviations for the <i>k</i>_cat and <i>K</i>_M values are given in parentheses below the mean values obtained for triplicate experiments.</p

Data collection and refinement statistics for structures reported in this work.

<p>^*Values in parenthesis are for the highest-resolution shell.</p>†<p><i>R</i>_merge(I)  =  (Σ<i>_hkl</i> Σ<i>_j</i> |<i>I_hkl,j−</i>〈<i>I_hkl</i>〉|)/(Σ<i>_hkl</i> Σ<i>_j I_hkl,j</i>) where 〈<i>I_hkl</i>〉 is the average intensity of <i>j</i> symmetry-related observations of reflections with Miller indices <i>hkl</i>.</p>#<p>CC_1/2  =  percentage of correlation between intensities from random half-datasets.</p>‡<p><i>R</i>_work  =  Σ<i>_hkl</i>|F_(obs)−F_(calc)|/Σ<i>_hkl</i>|F_(obs)|; 5% of the data that were excluded from the refinement were used to calculate <i>R</i>_free.</p