Equine Butyrylcholinesterase Research Articles

Exploring new 5-Nitroimidazole Derivatives as Potent Acetylcholinesterase and Butyrylcholinesterase Enzyme Inhibitors.

Discovering new compounds capable of inhibiting physiologically and metabolically significant drug targets or enzymes is of paramount importance in biological chemistry. With this aim, new 5-nitroimidazole derivatives (1-4) were designed and synthesized, and their inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were discovered using acetyl (butyryl) thiocholine and Ellman's reagents for spectrophotometric assay. The inhibitory profiles of the synthesized compounds were assessed by comparing their IC50 and Ki values. Results demonstrate significant inhibitory activity of all synthesized compounds against both AChE and BuChE compared to the reference compound, donepezil. Notably, compound 4 exhibited dual inhibition of these enzymes, showing the highest activity against Electrophorus electricus AChE (EeAChE) with a Ki value of 0.024±0.009 nM and against equine BuChE (eqBuChE) with a Ki value of 0.087±0.017 nM. Furthermore, molecular modeling was conducted to study the interaction modes of the most potent compound (4) and donepezil in the active site of their related enzymes' crystal structures (PDB ID: 4EY7 and 4BDS, respectively). Additionally, drug-likeness, ADME, and toxicity profiles of the compounds and metronidazole were predicted. The above results indicated that the dual inhibition of these enzymes is considered as a promising strategy for the treatment of neurological disorder especially Alzheimer's disease.

Hydrazide‐Bridged Pyridazines for Cholinesterase Inhibitors: Synthesis, Characterizations, In Silico, and In Vitro Evaluation

AbstractIn this study, we investigate the inhibitory potential of a series of hydrazide derivatives bearing different substituents with the pyridazine structure (5 a–i and 6 a–f) against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) using a modified Ellman's method. The inhibitory profiles of the synthesized compounds were assessed by comparing their IC50 and Ki values. Our results demonstrate that all the compounds exhibit significant inhibitory activity against both AChE and BChE when compared to the reference compound, tacrine. Particularly, compound 6 a exhibited the highest activity against Electrophorus electricus AChE (EeAChE) with a Ki value of 3.26 nM, while compound 5 a displayed the most potent inhibition against equine BChE (eqBChE) with a Ki value of 0.94 nM. The compounds did not possess significant cytotoxicity action using the MTT assay on the cancer cell lines. The DPPH assays revealed that all the compounds have moderate antioxidant activities. Furthermore, molecular docking studies provided valuable insights into the interaction mechanisms of these compounds within the active sites of AChE and BChE crystal structures (PDB ID: 4EY7 and 4BDS, respectively). The above results indicated that the pyridazine‐based compounds were a promising functional agent for the treatment of Alzheimer's disease.

In-vitro and in-silico studies of annelated 1,4,7,8-tetrahydroazocine ester derivatives as nanomolar selective inhibitors of human butyrylcholinesterase

Based on previous finding showing 2,3,6,11-tetrahydro-1H-azocino[4,5-b]indole as suitable scaffold of novel inhibitors of acetylcholinesterase (AChE), a main target of drugs for the treatment of Alzheimer's disease and related dementias, herein we investigated diverse newly and previously synthesized β-enamino esters (and ketones) derivatives of 1,4,7,8-tetrahydroazocines (and some azonines) fused with benzene, 1H-indole, 4H-chromen-4-one and pyrimidin-4(3H)-one. Twenty derivatives of diversely annelated eight-to-nine-membered azaheterocyclic ring, prepared through domino reaction of the respective tetrahydropyridine and azepine with activated alkynes, were assayed for the inhibitory activity against AChE and butyrylcholinesterase (BChE). As a major outcome, compound 7c, an alkylamino derivative of tetrahydropyrimido[4,5-d]azocine, was found to be a highly potent BChE-selective inhibitor, which showed a noncompetitive/mixed-type inhibition mechanism against human BChE with single digit nanomolar inhibition constant (Ki = 7.8 ± 0.2 nM). The four-order magnitude BChE-selectivity of 7c clearly reflects the effect of lipophilicity upon binding to the BChE binding cavity. The ChEs’ inhibition data, interpreted by chemoinformatic tools and an in-depth in-silico study (molecular docking combined with molecular dynamics calculations), not only highlighted key structural factors enhancing inhibition potency and selectivity toward BChE, but also shed light on subtle differences distinguishing the binding sites of equine BChE from the recombinant human BChE. Compound 7c inhibited P-glycoprotein with IC50 of 0.27 μM, which may support its ability to permeate blood-brain barrier, and proved to be no cytotoxic in human liver cancer cell line (HepG2) at the BChE bioactive concentrations. Overall, the biological profile allows us to envision 7c as a promising template to improve design and development of BChE-selective ligands of pharmaceutical interest, including inhibitors and fluorogenic probes.

Arylboronic acids as safe and specific human butyrylcholinesterase inhibitors

The drug treatment of Alzheimer's disease (AD) remains a significant scientific challenge, necessitating a continual search for new drug candidates. In this context, we present here, for the first time, new oxime-arylboronic acid hybrids (L1-L6) as potential anti-AD agents. These hybrids were synthesized and evaluated for their inhibitory capabilities on the activity of non-human cholinesterases [Electrophorus electricus Acetylcholinesterase (EeAChE) and Equine Butyrylcholinesterase (EqBChE)] as well as human cholinesterases [erythrocyte Acetylcholinesterase (hAChE) and plasma Butyrylcholinesterase (hBChE)]. We also assessed the safety of these compounds in a microglia cell line and analyzed the compound-enzyme interactions using molecular docking and molecular dynamics simulations. All compounds were found to be safe for the tests conducted. None of them exhibited significant inhibitory activity against hAChE or EeAChE. However, L1-L5 demonstrated inhibition of EqBChE and hBChE, with L3 being the most potent inhibitor of hBChE (IC50 = 6.41 ± 0.62 µM) and EqBChE (IC50 = 81.28 ± 4.01 µM). Additionally, L2, L3, and L5 showed 8–15 times higher potency as inhibitors of hBChE compared to EqBChE. These findings indicate that the hybrid oxime-arylboronic acids act as specific inhibitors of BChE, with a notable selectivity for hBChE, making them promising structures for the development of more potent and selective hBChE inhibitors.

New Pyrimidine and Pyridine Derivatives as Multitarget Cholinesterase Inhibitors: Design, Synthesis, and In Vitro and In Cellulo Evaluation.

A new series of pyrimidine and pyridine diamines was designed as dual binding site inhibitors of cholinesterases (ChEs), characterized by two small aromatic moieties separated by a diaminoalkyl flexible linker. Many compounds are mixed or uncompetitive acetylcholinesterase (AChE) and/or butyrylcholinesterase (BChE) nanomolar inhibitors, with compound 9 being the most active on Electrophorus electricus AChE (EeAChE) (Ki = 0.312 μM) and compound 22 on equine BChE (eqBChE) (Ki = 0.099 μM). Molecular docking and molecular dynamic studies confirmed the interaction mode of our compounds with the enzymatic active site. UV–vis spectroscopic studies showed that these compounds can form complexes with Cu2+ and Fe3+ and that compounds 18, 20, and 30 have antioxidant properties. Interestingly, some compounds were also able to reduce Aβ42 and tau aggregation, with compound 28 being the most potent (22.3 and 17.0% inhibition at 100 μM on Aβ42 and tau, respectively). Moreover, the most active compounds showed low cytotoxicity on a human brain cell line and they were predicted as BBB-permeable.

Fine-Tuning the Biological Profile of Multitarget Mitochondriotropic Antioxidants for Neurodegenerative Diseases.

Neurotransmitter depletion and mitochondrial dysfunction are among the multiple pathological events that lead to neurodegeneration. Following our previous studies related with the development of multitarget mitochondriotropic antioxidants, this study aims to evaluate whether the π-system extension on the chemical scaffolds of AntiOXCIN2 and AntiOXCIN3 affects their bioactivity and safety profiles. After the synthesis of four triphenylphosphonium (TPP+) conjugates (compounds 2–5), we evaluated their antioxidant properties and their effect on neurotransmitter-metabolizing enzymes. All compounds were potent equine butyrylcholinesterase (eqBChE) and moderate electric eel acetylcholinesterase (eeAChE) inhibitors, with catechols 4 and 5 presenting lower IC50 values than AntiOXCIN2 and AntiOXCIN3, respectively. However, differences in the inhibition potency and selectivity of compounds 2–5 towards non-human and human cholinesterases (ChEs) were observed. Co-crystallization studies with compounds 2–5 in complex with human ChEs (hChEs) showed that these compounds exhibit different binging modes to hAChE and hBChE. Unlike AntiOXCINs, compounds 2–5 displayed moderate human monoamine oxidase (hMAO) inhibitory activity. Moreover, compounds 4 and 5 presented higher ORAC-FL indexes and lower oxidation potential values than the corresponding AntiOXCINs. Catechols 4 and 5 exhibited broader safety windows in differentiated neuroblastoma cells than benzodioxole derivatives 2 and 3. Compound 4 is highlighted as a safe mitochondria-targeted antioxidant with dual ChE/MAO inhibitory activity. Overall, this work is a contribution for the development of dual therapeutic agents addressing both mitochondrial oxidative stress and neurotransmitter depletion.

Interactions of dye compounds that are structurally related to methylene blue with acetylcholinesterase and butyrylcholinesterase

AbstractThe phenothiazine dye, methylene blue, is reported to be an inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Inhibitors of these enzymes are established medications for the treatment of Alzheimer's disease, whilst methylene blue has been investigated for its potential to slow cognitive decline in Alzheimer's disease. Based on these observations, 31 dye compounds that are structurally related to methylene blue were evaluated as inhibitors of human AChE and equine BuChE. This study attempted to derive structure–activity relationships for the inhibition of AChE and BuChE by dye compounds, whilst discovering good potency inhibitors amongst the dyes. The results showed that several dyes exhibit good potency AChE (11 compounds) and BuChE (15 compounds) inhibition with IC50 < 10 µM. Methylene green (IC50 = 0.467 µM) and new methylene blue N (IC50 = 0.799 µM) were found to be particularly potent AChE inhibitors, whilst acridine orange (IC50 = 0.220 µM), 1,9‐dimethyl‐methylene blue (IC50 = 0.277 µM), acridine yellow G (IC50 = 0.509 µM), Nile blue (IC50 = 0.678 µM) and pyronin B (IC50 = 0.946 µM) proved to be highly potent BuChE inhibitors. These dye compounds thus exhibit improved inhibition compared to methylene blue [IC50(AChE) = 2.74 μM; IC50(BuChE) = 2.27 μM].

N-1,2,3-triazole-isatin derivatives for cholinesterase and β-amyloid aggregation inhibition: A comprehensive bioassay study.

Our goal was the evaluation of a series of N-1,2,3-triazole-isatin derivatives for multi-target activity which included cholinesterase (ChE) inhibition and β-amyloid (Aβ) peptide anti-aggregation. The compounds have shown considerable promise as butyrylcholinesterase (BuChE) inhibitors. Although the inhibition of eel acetylcholinesterase (eeAChE) was weak, the inhibitions against equine BuChE (eqBuChE) and human BuChE (hBuChE) were more significant with a best inhibition against eqBuChE of 0.46μM. In some cases, these molecules gave better inhibitions for hBuChE than eqBuChE. For greater insights into their mode of action, molecular docking studies were carried out, followed by STD-NMR validation. In addition, some of these compounds showed weak Aβ anti-aggregation activity. Hepatotoxicity studies showed that they were non-hepatoxic and neurotoxicity studies using neurite outgrowth experiments led to the conclusion that these compounds are only weakly neurotoxic.

A novel method for the synthesis of 1,2,4-triazole-derived heterocyclic compounds: enzyme inhibition and molecular docking studies

Two series of new N-aryl/aralkyl derivatives (9a–q) of 2-(4-ethyl-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-ylthio)acetamide and N-aryl/aralkyl derivatives (10a–q) of 2-(4-phenyl-5-(thiophen-2-ylmethyl)-4H-1,2,4-triazol-3-ylthio)acetamide were synthesized. The methods included successive conversions of thiophen-2-acetic acid (a) into its respective ester, hydrazide and N-aryl/aralkyl 1,3,4-triazole. The target compounds (9a–q; 10a–q) were obtained by the reaction of N-aryl/aralkyl 1,3,4-triazole (5, 6) with various electrophiles, (8a–q), in N,N-dimethyl formamide (DMF) and sodium hydroxide at room temperature. The characterization of these compounds was done by FTIR, 1H-, 13C-NMR, EI-MS and HR-EI-MS spectral data. All compounds were evaluated for their enzyme inhibitory potentials against electric eel acetylcholinesterase, AChE (10f, 10d; IC50 values 32.26 ± 0.12, 45.72 ± 0.11 µM, respectively), equine butyrylcholinesterase, BChE (9d, 9l, 9b, 10d, 10h; IC50 values 12.52 ± 0.19, 12.52 ± 0.19, 21.72 ± 0.18, 23.62 ± 0.22, 24.52 ± 0.21 µM, respectively), jack bean urease (10i, 10n, 9e; IC50 values 7.27 ± 0.05, 7.35 ± 0.04, 8.79 ± 0.05 µM, respectively) and yeast α-glucosidase enzymes (9o, 10i; IC50 values 62.94 ± 0.19, and 69.46 ± 0.15 µM, respectively). The molecular docking studies supported these findings. This study provides cheaper bioactive triazole amides as promising future lead molecules.

Phenoxyethyl Piperidine/Morpholine Derivatives as PAS and CAS Inhibitors of Cholinesterases: Insights for Future Drug Design

Acetylcholinesterase (AChE) catalyzes the conversion of Aβ peptide to its aggregated form and the peripheral anionic site (PAS) of AChE is mainly involved in this phenomenon. Also catalytic active site (CAS) of donepezil stimulates the break-down of acetylcholine (ACh) and depletion of ACh in cholinergic synapses are well established in brains of patients with AD. In this study, a set of compounds bearing phenoxyethyl amines were synthesized and their inhibitory activity toward electric eel AChE (eeAChE) and equine butyrylcholinesterase (eqBuChE) were evaluated. Molecular dynamics (MD) was employed to record the binding interactions of best compounds against human cholinesterases (hAChE and hBuChE) as well as donepezil as reference drug. In vitro results revealed that compound 5c is capable of inhibiting eeAChE activity at IC50 of 0.50 µM while no inhibitory activity was found for eqBuChE for up to 100 µM concentrations. Compound 5c, also due to its facile synthesis, small structure and high selectivity for eeAChE would be very interesting candidate in forthcoming studies. The main interacting parts of compound 5c and compound 7c (most potent eeAChE and eqBuChE inhibitors respectively) with receptors which confer selectivity for AChE and BuChE inhibition were identified, discussed, and compared with donepezil’s interactions. Also during MD simulation it was discovered for the first time that binding of substrates like donepezil to dual CAS and PAS or solely CAS region might have a suppressive impact on 4-α-helical bundles near the tryptophan amphiphilic tetramerization (WAT) domain of AChE and residues which are far away from AChE active site. The results proposed that residues involved in donepezil interactions (Trp86 and Phe295) which are located in CAS and mid-gorge are the mediator of conformational changes in whole protein structure.

Novel pyridazinone derivatives as butyrylcholinesterase inhibitors

In the current study, forty-four new [3-(2/3/4-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl carbamate derivatives were synthesized and evaluated for their ability to inhibit electric eel acetylcholinesterase (EeAChE) and equine butyrylcholinesterase (eqBuChE) enzymes. According to the inhibitory activity results, [3-(2-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl heptylcarbamate (16c, eqBuChE, IC50 = 12.8 μM; EeAChE, no inhibition at 100 μM) was the most potent eqBuChE inhibitor among the synthesized compounds and was found to be a moderate inhibitor compared to donepezil (eqBuChE, IC50 = 3.25 μM; EeAChE, IC50 = 0.11 μM). Kinetic and molecular docking studies indicated that compounds 16c and 14c (hexylcarbamate derivative, eqBuChE, IC50 = 35 μM; EeAChE, no inhibition at 100 μM) were mixed-type inhibitors which accommodated within the catalytic active site (CAS) and peripheral anionic site (PAS) of hBuChE through stable hydrogen bonding and π-π stacking. Furthermore, it was determined that [3-(2-methoxyphenyl)-6-oxopyridazin-1(6H)-yl]methyl (4-methylphenyl)carbamate 7c (eqBuChE, IC50 = 34.5 μM; EeAChE, 38.9% inhibition at 100 μM) was the most active derivative against EeAChE and a competitive inhibitor binding to the CAS of hBuChE. As a result, 6-(2-methoxyphenyl)pyridazin-3(2H)-one scaffold is important for the inhibitory activity and compounds 7c, 14c and 16c might be considered as promising lead candidates for the design and development of selective BuChE inhibitors for Alzheimer’s disease treatment.

Tryptamine–Triazole Hybrid Compounds for Selective Butyrylcholinesterase Inhibition

Tryptamine–triazole hybrid compounds (11–18) were synthesized via click reaction between tryptamine azide and propargylated natural compounds. Their cholinesterase inhibitory activity was evaluated. Among the eight compounds, compound 11 showed the most potent inhibitory activity [IC50 = 0.42 ± 0.29 μM for equine butyrylcholinesterase (BuChE) and 1.96 ± 0.15 μM for human BuChE]. From the molecular modeling study, compound 11 was bound to the catalytic anionic site, anionic subsite, peripheral anionic subsite, acyl‐binding pocket, and oxyanion hole of human or horse BuChE by forming a hairpin or U‐shaped structure. The Lineweaver‐Burk plot of compound 11 against BuChE suggests a mixed type of inhibition which corresponds well with the molecular modeling study.

Alkaloid profiling, anticholinesterase activity and molecular modeling study of Galanthus elwesii

In this study, Galanthus elwesii Hook. (Amaryllidaceae) was investigated for its chemical composition by using GC-MS (Gas Chromatography-Mass Spectrometry) method and anticholinesterase activity together with molecular modeling studies. Galanthus elwesii was collected from three different regions of Turkey and 44 compounds were detected by GC-MS in six different alkaloid extracts. The molecular docking technique was carried out to exhibit binding orientations of Galanthus elwesii compounds in the gorge of the active site of acetylcholinesterase (AChE) of Electrophorus electricus and equine butyrylcholinesterase (BuChE) constituted from the crystal structure of human BuChE with the help of homology modeling technique. Interesting results were obtained from the docking study, especially on O-methylleucotamine. The AChE and BuChE inhibitory activities of the extracts were also tested by in vitro Ellman method. The samples collected from Karaburun-Izmir were found to be the most active among others.

New (benz)imidazolopyridino tacrines as nonhepatotoxic, cholinesterase inhibitors for Alzheimer disease.

Due to the multifactorial nature of Alzheimer's disease, there is an urgent search for new more efficient, multitarget-directed drugs. This paper describes the synthesis, antioxidant and in vitro biological evaluation of ten (benz)imidazopyridino tacrines (7-16), showing less toxicity than tacrine at high doses, and potent cholinesterase inhibitory capacity, in the low micromolar range. Among them, compound 10 is a nonhepatotoxic tacrine at 1000 mM, showing moderate, but totally selective electric eel acetylcholinesterase inhibition, whereas molecule 16 is twofold less toxic than tacrine at 1000 μM, showing moderate and almost equipotent inhibition for electric eel acetylcholinesterase and equine butyrylcholinesterase. (Benz)imidazopyridino tacrines (7-16) have been identified as a new and promising type of tacrines for the potential treatment of Alzheimer's disease.

Stereospecific cholinesterase inhibition by O,S-diethylphenylphosphonothioate

The inhibition kinetics and stereospecificity of the chiral nerve agent derivative O,S-diethylphenylphosphonothioate (DEPP) were examined for two forms of acetylcholinesterase (human and eel) and equine butyrylcholinesterase. Both S- and R-DEPP are poor inhibitors of eel AChE (IC50 150μM), consistent with a large, nondiscriminatory binding interaction in the active site of this enzyme. However, S-DEPP is active against human and equine AChE with low μM IC50s. DEPP stereospecificities (S/R) toward these enzymes are moderate (20) relative to other cholinesterase-organophosphate (OP) systems. Pralidoxime, a common rescue agent, affects a modest recovery of both hAChE and eqBChE from treatment with S-DEPP. This result is consistent with expected chemical modification by DEPP and indicates that a measurable amount of the enzyme-phosphonate adduct does not undergo aging. Kinetic analysis of inhibition of both hAChE and eqBChE by S-DEPP yields KI values near 8μM and k2 values of about 0.10min−1. In both cases, the reaction is practically irreversible. Second order rate constants calculated from these values are similar to those obtained previously using other thio-substituted OPs with bulky groups. Since BChE has a more accommodating acyl pocket than AChE, the similar behaviors of both enzymes toward S-DEPP is notable and is likely a reflection of the weakened potency of DEPP relative to chemical warfare agents.

Butyrylcholinesterase nanocapsule as a long circulating bioscavenger with reduced immune response

Butyrylcholinesterase (BChE) is the most promising bioscavenger candidate to treat or prevent organophosphate (OP) poisoning. However, the clinical application of BChE is limited by two obstacles: an inadequate circulation half-life and limited sources for production. Although several modification technologies including glycosylation and PEGylation have been developed to improve its pharmacokinetics, none of them have been able to outperform blood-derived native BChE. In this work, we designed a long-circulating bioscavenger nanogel by coating equine serum-derived BChE with a zwitterionic polymer gel layer. This zwitterionic gel coating protected BChE from denaturation and degradation under harsh conditions. Notably, the nanocapsule exhibited a long circulation half-life of ~45h, a three-fold increase from the unmodified native version, enabling both therapeutic and prophylactic applications. In addition, the gel coating reduced the immunogenicity of equine BChE, unlocking the possibility to use non-human derived BChE as an OP bioscavenger in humans.

Multipotent cholinesterase/monoamine oxidase inhibitors for the treatment of Alzheimer's disease: design, synthesis, biochemical evaluation, ADMET, molecular modeling, and QSAR analysis of novel donepezil-pyridyl hybrids.

The design, synthesis, and biochemical evaluation of donepezil-pyridyl hybrids (DPHs) as multipotent cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors for the potential treatment of Alzheimer’s disease (AD) is reported. The 3D-quantitative structure-activity relationship study was used to define 3D-pharmacophores for inhibition of MAO A/B, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) enzymes and to design DPHs as novel multi-target drug candidates with potential impact in the therapy of AD. DPH14 (Electrophorus electricus AChE [EeAChE]: half maximal inhibitory concentration [IC50] =1.1±0.3 nM; equine butyrylcholinesterase [eqBuChE]: IC50 =600±80 nM) was 318-fold more potent for the inhibition of AChE, and 1.3-fold less potent for the inhibition of BuChE than the reference compound ASS234. DPH14 is a potent human recombinant BuChE (hBuChE) inhibitor, in the same range as DPH12 or DPH16, but 13.1-fold less potent than DPH15 for the inhibition of human recombinant AChE (hAChE). Compared with donepezil, DPH14 is almost equipotent for the inhibition of hAChE, and 8.8-fold more potent for hBuChE. Concerning human monoamine oxidase (hMAO) A inhibition, only DPH9 and 5 proved active, compound DPH9 being the most potent (IC50 [MAO A] =5,700±2,100 nM). For hMAO B, only DPHs 13 and 14 were moderate inhibitors, and compound DPH14 was the most potent (IC50 [MAO B] =3,950±940 nM). Molecular modeling of inhibitor DPH14 within EeAChE showed a binding mode with an extended conformation, interacting simultaneously with both catalytic and peripheral sites of EeAChE thanks to a linker of appropriate length. Absortion, distribution, metabolism, excretion and toxicity analysis showed that structures lacking phenyl-substituent show better druglikeness profiles; in particular, DPHs13–15 showed the most suitable absortion, distribution, metabolism, excretion and toxicity properties. Novel donepezil-pyridyl hybrid DPH14 is a potent, moderately selective hAChE and selective irreversible hMAO B inhibitor which might be considered as a promising compound for further development for the treatment of AD.

2-Arachidonoylglycerol is a substrate for butyrylcholinesterase: A potential mechanism for extracellular endocannabinoid regulation

2-Arachidonoylglycerol (2-AG) is a component of the endocannabinoid receptor pathway and is primarily hydrolyzed by monoacylglycerol lipase (MAGL) in vivo. We found that the non-specific serine esterase, butyrylcholinesterase (BChE), can hydrolyze 2-AG with reasonable affinity and may present a new compensatory mechanism for endocannabinoid regulation. In vitro hydrolysis reactions of 2-AG with equine BChE were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) positive/negative electrospray ionization (ESI±) to measure the formation of arachidonic acid (AA) and the loss of 2-AG over time (min). The resulting Michaelis–Menten approximations reveal that BChE has affinity towards 2-AG in phosphate buffer at neutral pH (7.4). The calculated Vmax, Km and kcat were 12.1nmols−1, 57.5μM, and 0.074s−1, respectively, which produced a diffusion-controlled rate of association (kcat/Km) of 1.3×103M−1s−1. Human BChE 2-AG hydrolysis was measured by immunoprecipitating BChE from fresh plasma and monitoring 2-AG loss and AA formation over time. These findings show that BChE can hydrolyze 2-AG which may be evidence of a more specific role for BChE in endocannabinoid regulation.

The exploration of thienothiazines as selective butyrylcholinesterase inhibitors

The role of butyrylcholinesterase (BChE) in the progression of Alzheimer’s disease (AD) has recently become more crucial. In the AD brain, selective BChE inhibitors have been demonstrated to have a beneficial effect in vivo, probably by recovering cholinergic activity and/or by restoring AChE:BChE activity ratios to the levels observed in the healthy brain. Thienothiazines are compounds sharing some structural features with phenothiazines, which are known to be potent BChE inhibitors. Thus, in this contribution 45 thienothiazines were investigated for their BChE inhibitory activity. Six of them were proven to be potent and selective inhibitors of equine BChE’s hydrolase activity. Structure–activity relationships were laid out, and a tentative pharmacophore model for BChE inhibitors of the thienothiazine type was proposed. The most active compound, 3f, displayed a mixed type of inhibition and was also active against the human BChE (huBChE) with an IC50 huBChE of 0.51±0.07μM. Computational studies suggested that 3f likely binds to the catalytic site and nearby to the peripheral site of the huBChE in an extended form. In addition, the chemical space occupied by the active thienothiazines, as opposed to phenothiazines and other representative chemical classes of BChE inhibitors, was explored with the aid of ChemGPS-NP, and the relevant chemical space regions were identified. This study shows for the first time that thienothiazines represent a new group of BChE inhibitors that can be used as molecular probes for studying the role of BChE in the brain or for developing newer drug leads for AD therapy.

Development of a LC/MS/MS method to analyze butyrylcholinesterase inhibition resulting from multiple pesticide exposure

A hybrid LC/MS/MS and proteomics method was developed for the assessment of multiple pesticide exposure. The methodology was based on the analysis of tryptic peptides resulting from inhibited butyrylcholinesterase (BChE) after exposure to pesticides including organophosphates (OPs) and carbamates (CBs). The primary advantage of the assay was its ability to simultaneously examine multiple pesticide exposures in a single analytical experiment. Application of tandem and MS 3 techniques provided identities of the inhibiting pesticide, confirmation and localization of the site of inhibition and relative quantification of phosphorylated peptides present in tryptic digests of equine BChE (eBChE).