- Balancing Specificity and Promiscuity in Enzyme Evolution: Multidimensional Activity Transitions in the Alkaline Phosphatase Superfamily
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Highly proficient, promiscuous enzymes can be springboards for functional evolution, able to avoid loss of function during adaptation by their capacity to promote multiple reactions. We employ a systematic comparative study of structure, sequence, and sub
- Van Loo, Bert,Bayer, Christopher D.,Fischer, Gerhard,Jonas, Stefanie,Valkov, Eugene,Mohamed, Mark F.,Vorobieva, Anastassia,Dutruel, Celine,Hyv?nen, Marko,Hollfelder, Florian
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supporting information
p. 370 - 387
(2019/01/08)
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- Synthesis and anti-acetylcholinesterase properties of novel β- And γ-substituted alkoxy organophosphonates
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Activated organophosphate (OP) insecticides and chemical agents inhibit acetylcholinesterase (AChE) to form OP-AChE adducts. Whereas the structure of the OP correlates with the rate of inhibition, the structure of the OP-AChE adduct influences the rate at
- Kaleem Ahmed,Belabassi, Yamina,Sankaranarayanan, Lakshmi,Chao, Chih-Kai,Gerdes, John M.,Thompson, Charles M.
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p. 2048 - 2051
(2013/04/23)
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- CHOLINESTERASE INHIBITORS
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The invention provides compounds that inhibit cholinesterases, such as acetylcholinesterase and butyrylcholinesterase. Such compounds are useful to prevent or treat exposure of a patient (e.g., a human) to an organophosphoric nerve agent (e.g., sarin and
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Paragraph 0139-0141
(2014/02/15)
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- Mechanistic study of Protein Phosphatase-1 (PP1), a catalytically promiscuous enzyme
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The reaction catalyzed by the protein phosphatase-1 (PP1) has been examined by linear free energy relationships and kinetic isotope effects. With the substrate 4-nitrophenyl phosphate (4NPP), the reaction exhibits a bell-shaped pH-rate profile for kcat/KM indicative of catalysis by both acidic and basic residues, with kinetic pKa values of 6.0 and 7.2. The enzymatic hydrolysis of a series of aryl monoester substrates yields a Bronsted βlg of -0.32, considerably less negative than that of the uncatalyzed hydrolysis of monoester dianions (-1.23). Kinetic isotope effects in the leaving group with the substrate 4NPP are 18(V/K)bridge = 1.0170 and 15(V/K) = 1.0010, which, compared against other enzymatic KIEs with and without general acid catalysis, are consistent with a loose transition state with partial neutralization of the leaving group. PP1 also efficiently catalyzes the hydrolysis of 4-nitrophenyl methylphosphonate (4NPMP). The enzymatic hydrolysis of a series of aryl methylphosphonate substrates yields a Bronsted βlg of -0.30, smaller than the alkaline hydrolysis (-0.69) and similar to the βlg measured for monoester substrates, indicative of similar transition states. The KIEs and the βlg data point to a transition state for the alkaline hydrolysis of 4NPMP that is similar to that of diesters with the same leaving group. For the enzymatic reaction of 4NPMP, the KIEs are indicative of a transition state that is somewhat looser than the alkaline hydrolysis reaction and similar to the PP1-catalyzed monoester reaction. The data cumulatively point to enzymatic transition states for aryl phosphate monoester and aryl methylphosphonate hydrolysis reactions that are much more similar to one another than the nonenzymatic hydrolysis reactions of the two substrates.
- McWhirter, Claire,Lund, Elizabeth A.,Tanifum, Eric A.,Feng, Guoqiang,Sheikh, Qaiser I.,Hengge, Alvan C.,Williams, Nicholas H.
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experimental part
p. 13673 - 13682
(2009/02/06)
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- One pot synthesis of diastereomeric phosphonates
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The reaction of diaryl methylphosphonate with sterically hindered alcohols in presence of sodium hydride provide arylalkyl methylphosphonate esters with high diastereoselectivity at the phosphorus center.
- Saxena, Shefali,Sharma, Mamta,Purnanand
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p. 259 - 266
(2007/10/03)
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- 1,8-Diazabicyclo[5.4.0]undecene mediated transesterification of p-nitrophenyl phosphonates: A novel route to phosphono esters
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DBU (1,8-diazabicyclo[5.4.0]undecene) was found to efficiently mediate the transesterification of p-nitrophenyl (PNP) phosphonates by various alcohols. The reactions of bis-PNP phosphonates in the presence of DBU, using both primary and secondary alcohols, phenols and amines, proceed rapidly and with high yield to afford the corresponding monoalkyl/aryl mono-PNP phosphonates as sole products (1, Scheme 2). The resulting monoalkyl/aryl mono-PNP phosphonates can be further reacted with a second alcohol to give the corresponding differently disubstituted phosphonates 3, or selectively hydrolysed to yield the monoalkyl/aryl phosphonic acids 2. We have applied this chemistry to the preparation of a series of phosphono ester transition state analogues 11a-e (Scheme 3) that were used as haptens for raising catalytic antibodies.
- Tawfik,Eshhar,Bentolila,Green
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p. 968 - 972
(2007/10/02)
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- Rate-Determining Carbonyl Hydration in the Intramolecular Hydrolysis of Phenacyl Phosphonate Esters: Isotopic Probes and Activation Parameters
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4-Nitrophenyl 4-substituted-phenacyl methylphosphonate esters (CH3, H, CH3O, NO2, and Cl) decompose in aqueous buffers 1-4 orders of magnitude faster than analogs with alkoxy substituents not containing a β-carbonyl group.This is consistent with an intramolecular displacement of 4-nitrophenol by the anion of the carbonyl hydrate. 18O incorporation into the hydrolysis product of the 4-CH3 derivative from H2(18O) in alkaline solution is 50percent.This indicates a rapid protonic equilibrium between the carbonyl hydrate and the medium but slower equilibration of the carbonyl O with the medium than cyclization.General base-catalyzed water attack in formation of the carbonyl hydrate is rate determining followed by cyclization with a rate constant >106 s-1.Supportive evidence is provided by buffer dependence, small normal solvent isotope effects, effect of 4-substituents in the phenacyl group (ρ=1.83+/-0.15), and activation parameters ΔH=49+/-2 kJ/mol and ΔS=-118+/-6 J/(mol K) for the phosphate dianion-catalyzed reaction and ΔH=21.5+/-0.8 kJ/mol and ΔS=183+/-3 J/(mol K) for the Tris base-catalyzed reaction.Inverse dependence of the rate constants for the phosphate dianion-catalyzed reaction on increasing ionic strength and solvent polarity also support the proposed mechanism.The solvent isotope effect for nucleophilic addition of increasing concentrations of lyoxide ion decreases from ca.2.0 to 0.9.The normal effect may indicate significant solvent restructuring as the negative charge is redistributed at the transition state in dilute solutions of lyoxide ion.The activation parameters for the reaction of hydroxide ion are ΔH=35.9+/-0.1 kJ/mol and ΔS=-59.8+/-0.4 J/(mol K).The compounds have a built-in trap for the carbonyl hydrate formed with instantaneous release of a signal molecule, 4-nitrophenol, and thus are ideally suited for the measurement of hydration rates of aryl alkyl ketones.
- Kovach, Ildiko M.,Zhao, Qinjian,Keane, Matthew,Reyes, Rachel
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p. 10471 - 10476
(2007/10/02)
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