Metabolism of Chiral Ionylideneacetic Acids on the Abscisic Acid Biosynthetic Pathway in Cercospora

A Chiralcel OJ column was used to determine the absolute configuration of naturally occurring α-ionylideneacetic acid from Cercospora rosicola and γ-ionylideneacetic acid from C. cruenta as (R) enantiomers in accordance with their biosynthetic product, (S)-ABA. Both enantiomers of [1, 2-¹³C₂]-α and γ-ionylideneacetic acids were prepared and fed to C. rosicola and C. cruenta. Six combinations of feeding experiments comparatively and unequivocally demonstrated stereoselectivity in the biosynthetic conversions, including stepwise hydroxylation at C-1′ and 4′. Enzymatic isomerization from the γ to α-intermediate was suggested not to be involved in ABA biosynthesis in C. rosicola.     

Stereoselective Inhibition of Cholesterol Esterase by Enantiomers of <Emphasis Type="Italic">exo</Emphasis>- and <Emphasis Type="Italic">endo</Emphasis>-2-Norbornyl-<Emphasis Type="Italic">N</Emphasis>–<Emphasis Type="Italic">n</Emphasis>-butylcarbamates

Four stereoisomers of 2-norbornyl-N–n-butylcarbamates are characterized as the pseudo substrate inhibitors of cholesterol esterase. Cholesterol esterase shows enantioselective inhibition for enantiomers of exo- and endo-2-norbornyl-N–n-butylcarbamates. For the inhibitions by (R)-(+)- and (S)-(−)-exo-2-norbornyl-N–n-butylcarbamates, the R-enantiomer is 6.8 times more potent than the S-enantiomer. For the inhibitions by (R)-(+)- and (S)-(−)-endo-2-norbornyl-N–n-butyl-carbamates, the S-enantiomer is 4.6 times more potent than the R-enantiomer. The enzyme-inhibitor complex models have been proposed to explain these different enantioselectivities.     

Preferential catabolism of the (S)-enantiomer of the herbicide napropamide mediated by the enantioselective amidohydrolase SnaH and the dioxygenase Snpd in Sphingobium sp. strain B2

The (R)- and (S)-enantiomers of the chiral herbicide napropamide (NAP) show different biological activities and ecotoxicities. These two enantiomers behave differently in the environment due to enantioselective catabolism by microorganisms. However, the molecular mechanisms underlying this enantioselective catabolism remain largely unknown. In this study, the genes (snaH and snpd) involved in the catabolism of NAP were cloned from Sphingobium sp. B2, which was capable of catabolizing both NAP enantiomers. Compared with (R)-NAP, (S)-NAP was much more rapidly transformed by the amidase SnaH, which initially cleaved the amide bonds of (S)/(R)-NAP to form (S)/(R)-2-(1-naphthalenyloxy)-propanoic acid [(S)/(R)-NP] and diethylamine. The α-ketoglutarate-dependent dioxygenase Snpd, showing strict stereoselectivity for (S)-NP, further transformed (S)-NP to 1-naphthol and pyruvate. Molecular docking and site-directed mutagenesis analyses revealed that when the (S)-enantiomers of NAP and NP occupied the active sites, the distance between the ligand molecule and the coordination atom was shorter than that when the (R)-enantiomers occupied the active sites, which facilitated formation of the transition state complex. This study enhances our understanding of the preferential catabolism of the (S)-enantiomer of NAP on the molecular level.     

Solvent effect on the stereoselective addition reaction of optically active amines to N-methylphenylalanine N-carboxyanhydride

The effect of solvent on stereoselectivity in the nucleophilic addition reaction of various optically active amines to N-methylphenylalanine N-carboxyanhydride has been investigated. In m-dimethoxybenzene as solvent, (S)-valine, (S)-leucine, and (S)-phenylalanine ethyl esters reacted preferentially with (R)-N-methylphenylalanine N-carboxyanhydride, but the stereoselectivity decreased considerably in nitrobenzene and dimethylacetamide as solvents. In the latter solvents, the dipolar interactions between an amine and an N-carboxyanhydride and the orientation of the substituent of N-carboxyanhydride were seriously affected, hence the stereoselectivity decreased. As a consequence, the enantiomer selection by the terminal amine of a growing chain in the nucleophilic addition-type polymerization of α-amino acid N-carboxyanhydride can be controlled by the choice of solvent. (S)-Proline ethyl ester and (S)-α-phenylethylamine reacted preferentially with (S)-N-methylphenylalanine N-carboxyanhydride in m-dimethoxybenzene, and this type of selectivity did not change in nitrobenzene. But in dimethylacetamide the stereoselectivity decreased. In the transition state of the reaction of these amines and N-methylphenylalanine N-carboxyanhydride dipolar interactions are operating, which should be destroyed by dimethylacetamide but may not be affected by nitrobenzene.     

Steady‐State Plasma Concentration of Donepezil Enantiomers and Its Stereoselective Metabolism and Transport In Vitro

The aim of the present study was to elucidate the differences in the plasma concentration of two enantiomers of donepezil in Chinese patients with Alzheimer's disease (AD) and investigate in vitro stereoselective metabolism and transport. Donepezil enantiomers were separated and determined by LC‐MS/MS using D5‐donepezil as an internal standard on a Sepax Chiralomix SB‐5 column. In vitro stereoselective metabolism and transport of donepezil were investigated in human liver microsomes and MDCKII‐MDR1 cell monolayer. Pre‐dose (Css‐min) plasma concentrations were determined in 52 patients. The mean plasma level of (R)‐donepezil was 14.94 ng/ml and that of (S)‐donepezil was 23.37 ng/ml. One patient's plasma concentration of (R)‐donepezil was higher than (S)‐donepezil and the ratio is 1.51. The mean plasma levels of (S)‐donepezil were found to be higher than those of (R)‐donepezil in 51 patients and the ratio of plasma (R)‐ to (S)‐donepezil varies from 0.34 to 0.85. In the in vitro microsomal system, (R)‐donepezil degraded faster than (S)‐donepezil. V_max of (R)‐donepezil was significantly higher than (S)‐donepezil. The P‐gp inhibition experiment shown that the P_app of the two enantiomers was higher than 200 and the efflux ratios were 1.11 and 0.99. The results of the P‐gp inhibition identification experiment showed IC50 values of 35.5 and 20.4 μM, respectively, for the two enantiomers. The results indicate that donepezil exhibits stereoselective hepatic metabolism that may explain the differences in the steady‐state plasma concentrations observed. Neither (R)‐ nor (S)‐donepezil was a P‐gp substance and the two enantiomers are highly permeable through the blood–brain barrier. Chirality 25:498–505, 2013. © 2013 Wiley Periodicals, Inc.     

东亚飞蝗山西两地理种群酯酶特性的比较研究

对东亚飞蝗山西临猗和永济2个地理种群的酯酶特性进行了比较研究。非变性聚丙烯酰胺凝胶电 泳图谱显示：以α-乙酸萘酯为底物染色,2个东亚飞蝗种群谱带差别不明显。但是,酯酶动力 学研究结果表明：以α-乙酸萘酯和α-丁酸萘酯为底物时,永济种群的酯酶活性分别是临猗 种群的1.81倍和1.20倍。永济种群酯酶活性的增高可能与非变性聚丙烯酰胺凝胶电泳图谱显 示出较临猗种群多出的酶带有关。体外酯酶抑制动力学研究表明：永济和临猗2种群所含酯酶大 都为B型酯酶,其含量分别为84.94%和91.47%。永济种群对对氧磷的耐受性要高于临猗种群 ,我们推测可能与2种群马拉硫磷使用背景不同有关。     

Esterase Activities of Brevihacterium sp. R312 and Brevihacterium linens 62

Esterase activity of Brevihacterium linens 62 and Brevibacterium sp. R312 was detected. Each strain had esterase activities that hydrolyzed p-nitrophenyl acetate and α-naphthyl acetate. Biosynthesis and optimum pH and temperature of the two esterase activities showed that the latter were caused by different esterases. The influence of the culture medium and the growth substrate on biosynthesis of the esterase systems were studied. Hydrolysis of methylthioacetate and phenethyl acetate by cell extracts of the two strains was done. No enzymatic ester synthesis reaction was observed. However, transfer reactions by cell extracts of the two strains were done.     

Characterization of the esterase isozymes of Ips typographus (coleoptera,scolytidae)

Four esterase isozymes hydrolyzing α-naphthyl acetate (α-NA) were detected screening whole body homogenates of larvae and adults of Ips typographus by electrophoresis. Two of the four isozymes (isozymes 3 and 4) were not detected by α-NA staining in the pupal stage, but topical application of juvenile hormone III (JH III) on the pupa induced these isozymes. The JH esterase (JHE) activity on the gel was associated with the proteins of isozyme 2. The compounds OTFP, PTFP, and DFP inhibited this catalytic activity of isozyme 2 on the gel at low concentrations, whereas the proteins of isozyme 3 and 4 were affected only at higher concentrations. A quantitative developmental study was performed to characterize which of the esterases hydrolyzed JH III, using a putative surrogate substrate for JH (HEXTAT) and α-NA. The I₅₀ of several esterase inhibitors and the JH metabolites were also defined. All findings supported the results that a protein associated with isozyme 2 is catabolizing JH and that isozymes 3 and 4 are the main contributors to the general esterase activity on α-NA. The JHE from Tenebrio molitor was purified by affinity chromatography. Although the recovery was low, an analytical isoelectric focusing gel showed that the JHE activity of the purified enzyme. T. molitor cochromatographed at the same pl as the JHE activity of I. typographus. Arch. Insect Biochem. Physiol. 34:203–221, 1997. © 1997 Wiley-Liss, Inc.     

Stereoselective disposition of flurbiprofen from a mutual prodrug with a histamine H2-antagonist to reduce gastrointestinal lesions in the rat

The in vitro and in vivo stereoselective hydrolysis characteristics of the mutual prodrug FP-PPA, which is a conjugate of flurbiprofen (FP) with the histamine H₂-antagonist PPA, to reduce gastrointestinal lesions induced by FP were investigated and compared with those of FP methyl ester (rac-FP-Me) and FP ethyleneglycol ester (rac-FP-EG). The rac-FP derivatives were hydrolyzed preferentially to the (+)-S-isomer in plasma and to the (−)-R-isomer in liver and small intestinal mucosa. Interestingly, in the gastric mucosa, the stereoselectivity of hydrolysis of (−)-R-FP-PPA was opposite from that of rac-FP-Me and rac-FP-EG, which suggested that the stereoselective hydrolysis of FP-PPA was helpful in reducing gastric damage induced by (+)-S-FP. However, hydrolysis of all rac-FP derivatives was found to be catalyzed by carboxylesterases in the gastric mucosa. The stereoselective disposition of FP enantiomers early after intravenous administration of rac-FP-PPA could be explained by the stereoselective formation of (−)-R-FP from rac-FP-PPA in the liver. (−)-R-FP-PPA was completely hydrolyzed to form (−)-R-FP in vivo, while 78% of (+)-S-FP-PPA was hydrolyzed to (+)-S-FP, with a corresponding decrease in the area under the curve. Twenty-five percent of (+)-S-FP-PPA might be eliminated as the intact prodrug or its metabolites other than FP. The most important bioconversion of FP-PPA occurred in plasma, and additional hydrolysis of the R-enantiomer in liver resulted in the stereoselectivity observed following both i.v. and p.o. administration. © 1996 Wiley-Liss, Inc.     

Stereoselective hydrolysis of xenobiotic esters by different cell lines from rat liver and hepatoma and its application to chiral prodrugs for designated growth suppression of cancer cells

Stereoselectivity in the hydrolysis of racemic ethyl 2-phenylacetate derivatives by cultured cells of noncancerous cell lines from rat liver (BRL, BRL 3A, Clone 9, and ARLJ301–3), spontaneously or oncogene transformed rat liver cell lines (ARLJ301–3TR1, Anr4, Anr9–1, and Anr13–1), and cancer cell lines from rat hepatoma (H4-II-E, McA-RH7777, and MH₁C₁) and sarcoma (XC) was studied. A strong (R)-enantiomer preference was found in the hydrolysis of ethyl 2-hydroxy- ( 2c ) and 2-methoxy-2-phenylacetate ( 3c ) by the noncancerous and oncogene-transformed cells and an (S)-enantiomer preference for ethyl N-acylphenylalaninates with all the present cell lines. These inclinations were, however, not recognized with ethyl 2-methoxy-2-phenylpropanoate and ethyl N-difluoroacetyl-or N-trifluoroacetylphenylalaninate. Moreover, the R preference for 3c was reversed in the reaction by hepatoma cells. Thus, the stereoselectivity is influenced by both structure of acyl group and species of cell lines. The hepatoma cells were considerably different from the noncancerous or oncogene-transformed cells in stereoselectivity. This fact was consistent with the order of colony formation in soft agar cultures (index of malignancy) and the resemblance in actively stained esterase patterns in gel electrophoresis. The stereoselective hydrolysis leads to cell-specific activation of anticancer prodrugs. This has been confirmed for the first time by the stereoselectivity of Anr4 and H4-II-E cells in the hydrolysis of a chiral mustard ester, bis(2-chloroethyl)aminophenyl 2-methoxy-2-phenylacetate ( 14 ) and by the difference of IC₅₀ values of (R)- and (S)- 14 against the two cell lines. © 1995 Wiley-Liss, Inc.     

Supramolecular chirality transfer in a stereodynamic catalysts

We present rhodium catalysts that contain stereodynamic axially chiral biphenol‐derived phosphinite ligands modified with non‐stereoselective amides for non‐covalent interactions. A chirality transfer was achieved with (R)‐ or (S)‐acetylphenylalanine methyl amide, and the interaction mechanism was investigated by NMR measurements. These interactions at the non‐stereoselective interaction sites and the formation of supramolecular complexes result in an enrichment of either the (R_ax)‐ or (S_ax) enantiomer of the tropos catalysts, which in turn provide the (R)‐ or (S)‐acetylphenylalanine methyl ester in the hydrogenation of (Z)‐methyl‐α‐acetamidocinnamate.     

Role of juvenile hormone metabolism during embryogenesis of the house cricket,Acheta domesticus

The duration of embryogenesis was 9.5 days for house crickets, Acheta domesticus (L.), reared at 35°C. The major route of juvenile hormone (JH) metabolism was ester hydrolysis. The level of α-naphthyl acetate (α-NA) esterase activity per mg wet weight remained relatively constant throughout embryogenesis and was similar to that of eggs dissected from the oviducts. JH esterase activity per mg wet weight was highest in the dissected and day-1 eggs, declined to one-third of this peak activity by day 5, and then remained unchanged through hatching. Two populations of esterases (130,000 and > 200,000 in molecular weight) which metabolized JH and α-NA were resolved in day-1 eggs by gel filtration chromatography. Specific JH esterase appeared by day 4 with a molecular weight of 200,000. Correlative evidence is presented from other insect species that supports a functional role for JH metabolism during embryo development.     

Purification and properties of ap-nitrobenzyl esterase fromBacillus subtilis

A procedure for purifying to homogeneity a microbially produced biocatalyst useful for deblocking intermediates in the manufacture of beta-lactam antibiotics is reported. In aqueous solution the purifiedp-nitrobenzyl (PNB) carboxy-esterase was soluble, monomeric (molecular weight: 54 000 by SDS-PAGE or by gel filtration) and exhibited an acidic pl, 4.1. The PNB carboxy-esterase catalyzed rapid ester hydrolysis for simple organic esters such as PNB-acetate, benzyl acetate and -naphthyl acetate and catalyzed deblocking (ester hydrolysis) of beta-lactam antibiotic PNB esters such as cephalexin-PNB and loracarbef-PNB. TheN-terminal amino acid sequence and the amino acid composition are reported. A serine residue is involved in ester hydrolysis: the PNB carboxy esterase was inhibited by phenylmethylsulfonyl fluoride and diethylp-nitrophenyl phosphate; one mole of diisopropyl fluorophosphate titration was required per mole of PNB carboxy-esterase for complete inhibition. When the [³H]-diisopropyl fluorophosphate-treated biocatalyst was digested with Lys C and the resulting peptides separated by HPLC, a single [³H]-labeled peptide was obtained; its amino acid sequence is reported. Inhibition of the PNB carboxy esterase by diethyl pyrocarbonate suggests that a histidinyl residue (or residues) is (are) also involved in the catalytic site of the esterase.Abbreviations used -ME -mercaptoethanol - Cf cefaclor - Cf nucleus-PNB - (6R, 7R) 7-amino-3-chloro-8-oxo-5-thia-1-azabicyclo[4.2.0]-oct-2-ene-2-carboxylic acid, (4-nitrophenyl)methyl ester - Cp cephalexin - Cp-PNB p-nitrobenzyl carboxy-ester of cephalexin - DEPC diethyl, pyrocarbonate - DFP diisopropyl fluorophosphate - DMSO dimethyl sulfoxide - DNP diethylp-nitrophenyl phosphate - EDTA ethylenediaminetetraacetic acid - EGTA ethylene, glycol-bis(aminoethyl ether) - N,N,NN tetracetic acid - Lc loracarbef - Lc-PNB p-nitrobenzyl carboxy-ester of loracarbef - Lc nucleus-PNB - (6R, 7S) 7-amino-3-chloro-8-oxo-1-azabicyclo[4.2.0]-oct-2-ene-2-carboxylic acid, (4-nitrophenyl)methyl ester - Lys C an endoproteinase specifically cleaving at C terminal lysine residues - MW_r relative molecular weight - PAGE polyacrylamide gel electrophoresis - PMSF phenylmethylsulfonylfluoride - PNB p-nitrobenzyl - PNBCE p-nitrobenzyl carboxy-esterase - SDS sodium dodecyl sulfate     

Functional characterization of salt‐tolerant microbial esterase WDEst17 and its use in the generation of optically pure ethyl (R)‐3‐hydroxybutyrate

The two enantiomers of ethyl 3‐hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)‐3‐hydroxybutyrate. Herein, we also functionally characterized one novel salt‐tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)‐3‐hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio‐selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates.     

Input rate-dependent stereoselective pharmacokinetics: Effect of pulsatile oral input

Computer simulation was used to test the effects of pulsatile oral input on the stereoselectivity in the area under the blood concentration–time curves (AUCs) of the enantiomers of racemic drugs. The effects of input rate determinants, namely, dose, dosage interval, and formulation on the stereoselectivity were investigated under both steady-state and nonsteady-state conditions. Simulations were carried out for drugs undergoing Michaelis–Menten hepatic metabolism with different enantiomeric maximum velocity (V_max) or constant (K_m) values. With pulsatile input, the enantiomeric AUC ratios of both types of drugs were dependent on all the determinants of input rate. However, in most cases, the direction of input rate-dependent changes in the enantiomeric AUC ratios for drugs with different enantiomeric V_max was opposite of that for drugs with different enantiomeric K_m. The direction and magnitude of changes in the enantiomeric AUC ratios were also dependent on the selected dose, dosage interval, and formulation. Further, different conclusions could be reached based on the nonsteady-state and steady-state data. Additional simulations were then performed to test the effects of input rate-dependent stereoselective pharmacokinetics on the bioequivalence of chiral drugs with nonlinear metabolism. These simulations suggested that bioequivalence studies based on the racemic drug measurement may result in erroneous conclusions for the individual enantiomers. The results of this study may be used as a tool for the design of experiments to test the input rate dependence of stereoselective pharmacokinetics and bioequivalence of racemic drugs in animals and humans. © 1994 Wiley-Liss, Inc.     

Studies on the Syntheses of the Pyrethrin Analogues and their Biological Activities

The separation of (±) -2,2-dimethyl-3- (3′,4′-methylenedioxyphenyl) -cyclopropane-1-carboxylic acid into the geometrical isomers and the assignment of their configurations were achieved. Of the two isomers, the (±) -trans-acid, which was found more toxic when esterified with (±) -allethrolone, was resolved by means of an optically active α-phenylethylamine salt into (+) - and (-) -enantiomers. (IR:3R) -Configuration was assigned to the (+) -trans-acid and (IS:3S) -configuration to the (-) -trans-acid. The bioassay revealed that the (±) -allethrolone ester with the (+) -trans-acid, which belongs to the same optical series as the natural chrysanthemum acids, was the most toxic against common houseflies, as was the case with other pyrethroids.     

Stereoselective metabolism of fenoxaprop‐ethyl and its chiral metabolite fenoxaprop in rabbits

The stereoselective metabolism of the enantiomers of fenoxaprop‐ethyl (FE) and its primary chiral metabolite fenoxaprop (FA) in rabbits in vivo and in vitro was studied based on a validated chiral high‐performance liquid chromatography method. The information of in vivo metabolism was obtained by intravenous administration of racemic FE, racemic FA, and optically pure (−)‐(S)‐FE and (+)‐(R)‐FE separately. The results showed that FE degraded very fast to the metabolite FA, which was then metabolized in a stereoselective way in vivo: (−)‐(S)‐FA degraded faster in plasma, heart, lung, liver, kidney, and bile than its antipode. Moreover, a conversion of (−)‐(S)‐FA to (+)‐(R)‐FA in plasma was found after injection of optically pure (−)‐(S)‐ and (+)‐(R)‐FE separately. Either enantiomers were not detected in brain, spleen, muscle, and fat. Plasma concentration–time curves were best described by an open three‐compartment model, and the toxicokinetic parameters of the two enantiomers were significantly different. Different metabolism behaviors were observed in the degradations of FE and FA in the plasma and liver microsomes in vitro, which were helpful for understanding the stereoselective mechanism. This work suggested the stereoselective behaviors of chiral pollutants, and their chiral metabolites in environment should be taken into account for an accurate risk assessment. Chirality, 2011. © 2011 Wiley‐Liss, Inc.     

Polymerization of N-carboxyanhydrides of various α-amino acids using secondary amines as initiator

In the polymerizations of alanine, γ-ethyl glutamate, and leucine N-carboxyanhydrides (NCA's) initiated by tertiary amines and some secondary amines such as N-methyl-L -alanine dialkylamide, a stereoselectivity was observed: the polymerization rates of L - and D -NCA's were identical to each other and larger than that of DL -NCA. However, this selectivity was not observed in the polymerizations of valine and isoleucine NCA's initiated by N-methyl-L -alanine dialkylamide. The stereoselective polymerizations of valine and isoleucine NCA's were induced only with tetriary amines such as tri-n-butylamine. N-Methyl-L -alanine di-alkylamide has been shown to initiate the polymerization of usual α-amino acid NCA according to the activated-NCA mechanism, but it initiated the polymerizations of valine and isoleucine NCA's according to the primary amine-type mechanism. This is because in the latter NCA's the N–H group is masked by the adjacent C^β-branched alkyl substituent against the approach of the secondary amine. Poly(DL -alanine)s produced in the stereoselective polymerization had higher viscosities and were more stereoblock-like than those produced without the stereoselectivity. These experimental results indicate that the stereoselective polymerization is possible only when the polymerization proceeds through the activated-NCA mechanism.     

Evaluation of enantioselectivity in lipase-catalyzed acylation of hydroxyalkylphosphine oxides

The lipase-catalyzed optical resolution of 2-, 3-, and 5-hydroxyalkyl phosphorus compounds 1 provided the corresponding optically pure diastereomers in good yields. (S_P, R)- and (R_P, S)-1 were acylated faster than (S_P, S)- and (R_P, R)-1. The stereoselectivity at the phosphorus atom changed with the flexibility of the active sites in the lipases. The stereoselectivity at the phosphorus atom was higher in the reaction of 1a than in the reaction of 1b,c. The reaction rate of -hydroxyalkylphosphine oxide 1c was faster than that of 1a, although less enantioselectivity was observed at the phosphorus atom.     

东亚飞蝗山西两地理种群酯酶特性的比较研究

对东亚飞蝗山西临猗和永济2个地理种群的酯酶特性进行了比较研究.非变性聚丙烯酰胺凝胶电泳图谱显示:以a-乙酸萘酯为底物染色,2个东亚飞蝗种群谱带差别不明显.但是,酯酶动力学研究结果表明:以a-乙酸萘酯和α-丁酸萘酯为底物时,永济种群的酯酶活性分别是临猗种群的1.81倍和1.20倍.永济种群酯酶活性的增高可能与非变性聚丙烯酰胺凝胶电泳图谱显示出较临猗种群多出的酶带有关.体外酯酶抑制动力学研究表明:永济和临猗2种群所含酯酶大都为B型酯酶,其含量分别为84.94%和91.47%.永济种群对对氧磷的耐受性要高于临猗种群,我们推测可能与2种群马拉硫磷使用背景不同有关.