Butyrylcholinesterase inhibitory activity of testosterone and some of its metabolites

Testosterone and ten of its metabolites were examined as inhibitors of butyrylcholinesterase. A significant enzyme inhibition activity (IC₅₀ = 1.55 μM) was observed for androst-4-en-3,7-dione. The kinetic parameters of butyrylcholinesterase inhibition were determined and molecular docking was carried out in order to develop a better understanding of the inhibitor-enzyme interactions. The results showed that the inhibition was non-competitive, stabilized mainly by hydrogen bonds and hydrophobic interactions between the inhibitor and butyrylcholinesterase.     

Pharmacological effects of a novel isosorbide-based butyrylcholinesterase inhibitor

Isosorbide-2-benzylcarbamate-5-benzoate, a novel butyrylcholinesterase inhibitor, shows interspecies variation in its inhibitory activity (IC(50) of 4.3 nM for human plasma butyrylcholinesterase, but 1.09 microM for mouse plasma butyrylcholinesterase). Stability studies revealed that this drug is resistant to hydrolysis by human plasma (no degradation in 1 h). However, it was found to undergo rapid degradation when incubated with mouse plasma or mouse liver homogenate, yielding benzyl carbamate and benzoic acid. The addition of the carboxylesterase inhibitor bis-(4-nitrophenyl) phosphate (BNPP) inhibited the degradation of the novel drug, indicating that it may be a substrate for both butyrylcholinesterase and carboxylesterase. The absence of carboxylesterase from human plasma explains the drug's stability in this medium. In vivo, pharmacodynamic studies on single doses of 1 mg/kg to na?ve male C57BL/6 mice revealed maximal plasma butyrylcholinesterase inhibition 20 min after intraperitoneal administration (approximately 60% inhibition) and 1 h after administration by gavage (approximately 45% inhibition). While this plasma butyrylcholinesterase inhibition was short-lived, the drug also penetrated the blood-brain barrier resulting in a slight (10-15%) but persistent (> or =72 h) reduction in brain butyrylcholinesterase activity.     

Enzyme inhibition activities of the extracts from rhizomes of Gloriosa superba Linn (Colchicaceae)

An alcoholic extract obtained from the rhizomes of Gloriosa superba Linn (Colchicaceae) was screened for enzyme inhibition activities. The crude extract and its subsequent fractions including chloroform, ethyl acetate, n-butanol and aqueous were screened against lipoxygenase, actylcholinesterase, butyrylcholinesterase and urease. An outstanding inhibition on lipoxygenase was observed. The highest enzyme inhibition potency was expressed by the chloroform fraction (90%) among the tested fractions on lipoxygenase. Overall 67-90% inhibition was found for lipoxygenase, 46-69% for acetylcholinesterase and 10-33% for butyrylcholinesterase, while urease was not inhibited.     

家蚕系统表达的重组人丁酰胆碱酯酶的生化性质

研究家蚕系统中高效表达的重组人丁酰胆碱酯酶(rhBChE)的生化性质并与天然人丁酰胆碱酯酶(nhBChE)进行比较。采用丁酰胆碱酯酶活性测定,抑制剂及重活化剂作用,免疫印迹等方法。实验结果表明,rhBChE及nhBChE在底物亲和力、抑制剂敏感性及可重活化性、稳定性、对抗体的反应性等方面均有相似的生化性质,重组人丁酰胆碱酯酶具有天然人丁酰胆碱酯酶的功能。但rhBChE的糖基化修饰程度较低,用于人体时应予考虑     

Enzyme inhibition activities of the extracts from rhizomes of Gloriosa superba Linn (Colchicaceae)

An alcoholic extract obtained from the rhizomes of Gloriosa superba Linn (Colchicaceae) was screened for enzyme inhibition activities. The crude extract and its subsequent fractions including chloroform, ethyl acetate, n-butanol and aqueous were screened against lipoxygenase, actylcholinesterase, butyrylcholinesterase and urease. An outstanding inhibition on lipoxygenase was observed. The highest enzyme inhibition potency was expressed by the chloroform fraction (90%) among the tested fractions on lipoxygenase. Overall 67– 90% inhibition was found for lipoxygenase, 46-69% for acetylcholinesterase and 10–33% for butyrylcholinesterase, while urease was not inhibited.     

Inhibition activities of Colchicum luteum baker on lipoxygenase and other enzymes

In vitro enzymes inhibition activities of the crude methanolic extract and various fractions of Colchicum luteum Baker (Liliaceae) including chloroform, ethyl acetate, n-butanol and aqueous were carried out against actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease enzymes. A significant enzyme inhibition activity (89%) is shown by the crude methanolic extract and its fractions against lipoxygenase, while low to significant activity (32-75%) was evident against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity (29-61%) against acetylcholinesterase and no activity against urease.     

Kinetic analysis of effector modulation of butyrylcholinesterase-catalysed hydrolysis of acetanilides and homologous esters

The effects of tyramine, serotonin and benzalkonium on the esterase and aryl acylamidase activities of wild-type human butyrylcholinesterase and its peripheral anionic site mutant, D70G, were investigated. The kinetic study was carried out under steady-state conditions with neutral and positively charged aryl acylamides [o-nitrophenylacetanilide, o-nitrotrifluorophenylacetanilide and m-(acetamido) N,N,N-trimethylanilinium] and homologous esters (o-nitrophenyl acetate and acetylthiocholine). Tyramine was an activator of hydrolysis for neutral substrates and an inhibitor of hydrolysis for positively charged substrates. The affinity of D70G for tyramine was lower than that of the wild-type enzyme. Tyramine activation of hydrolysis for neutral substrates by D70G was linear. Tyramine was found to be a pure competitive inhibitor of hydrolysis for positively charged substrates with both wild-type butyrylcholinesterase and D70G. Serotonin inhibited both esterase and aryl acylamidase activities for both positively charged and neutral substrates. Inhibition of wild-type butyrylcholinesterase was hyperbolic (i.e. partial) with neutral substrates and linear with positively charged substrates. Inhibition of D70G was linear with all substrates. A comparison of the effects of tyramine and serotonin on D70G versus the wild-type enzyme indicated that: (a) the peripheral anionic site is involved in the nonlinear activation and inhibition of the wild-type enzyme; and (b) in the presence of charged substrates, the ligand does not bind to the peripheral anionic site, so that ligand effects are linear, reflecting their sole interaction with the active site binding locus. Benzalkonium acted as an activator at low concentrations with neutral substrates. High concentrations of benzalkonium caused parabolic inhibition of the activity with neutral substrates for both wild-type butyrylcholinesterase and D70G, suggesting multiple binding sites. Benzalkonium caused linear, noncompetitive inhibition of the positively charged aryl acetanilide m-(acetamido) N,N,N-trimethylanilinium for D70G, and an unusual mixed-type inhibition/activation (alpha > beta > 1) for wild-type butyrylcholinesterase with this substrate. No fundamental difference was observed between the effects of ligands on the butyrylcholinesterase-catalysed hydrolysis of esters and amides. Thus, butyrylcholinesterase uses the same machinery, i.e. the catalytic triad S198/H448/E325, for the hydrolysis of both types of substrate. The differences in response to ligand binding depend on whether the substrates are neutral or positively charged, i.e. the differences depend on the function of the peripheral site in wild-type butyrylcholinesterase, or the absence of its function in the D70G mutant. The complex inhibition/activation effects of effectors, depending on the integrity of the peripheral anionic site, reflect the allosteric 'cross-talk' between the peripheral anionic site and the catalytic centre.     

Enzyme inhibition activities of Andrachne cardifolia Muell

The crude methanolic extract and various fractions of Andrachne cardifolia Muell, including chloroform, ethyl acetate and n-butanol fractions were subjected to in vitro enzyme inhibition activity against acetylcholinesterase, butyrylcholinesterase, lipoxygenase and urease enzymes. A significant enzyme inhibition activity (40-89%) was shown by the crude methanolic extract and its fractions against lipoxygenase, while low to significant activity (40-71%) against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated poor to significant activity (25-73%) against acetylcholinesterase and no activity against urease.     

Inhibition of Human Blood Acetylcholinesterase and Butyrylcholinesterase by Some Alkaloids

A comparative study has been carried out on effects of berberine (diisoquinoline alkaloid) and sanguinarine and chelidonine (benzophenanthridine alkaloids( on erythrocyte acetylcholinesterase and serum butyrylcholinesterase from human blood. The studied alkaloids have been shown to be strong reversible inhibitors of the cholinesterase activity. Acetylcholinesterase is more sensitive to their action, than butyrylcholinesterase. The type of reversible inhibition was determined, and inhibitor constants were calculated. It is revealed that the character of inhibition is identical for the both cholinesterases. Berberine and sanguinarine are competitive-noncompetitive inhibitors, whereas chelidonine, a competitive inhibitor.     

Enzyme inhibition activities of Teucrium royleanum

The crude methanolic extract and chloroform, ethyl acetate and n-butanol fractions of Teucrium royleanum were examined as inhibitors of actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease. A significant enzyme inhibition activity (52-83%) was shown by the crude methanolic extract and its fractions against acetylcholinesterase, while low to outstanding enzyme inhibitory activity was shown (19-93%) against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity against lipoxygenase and inactive against urease.     

Inhibition activities of colchicum luteum baker on lipoxygenase and other enzymes

In vitro enzymes inhibition activities of the crude methanolic extract and various fractions of Colchicum luteum Baker (Liliaceae) including chloroform, ethyl acetate, n-butanol and aqueous were carried out against actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease enzymes. A significant enzyme inhibition activity (89%) is shown by the crude methanolic extract and its fractions against lipoxygenase, while low to significant activity (32–75%) was evident against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity (29–61%) against acetylcholinesterase and no activity against urease.     

Enzyme inhibition activities of teucrium royleanum

The crude methanolic extract and chloroform, ethyl acetate and n-butanol fractions of Teucrium royleanum were examined as inhibitors of actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease. A significant enzyme inhibition activity (52–83%) was shown by the crude methanolic extract and its fractions against acetylcholinesterase, while low to outstanding enzyme inhibitory activity was shown (19–93%) against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity against lipoxygenase and inactive against urease.     

Ethnic differences in the frequency of distribution of serum cholinesterase activity in the Iranian population

One thousand Iranians belonging to 5 different Iranian ethnic groups were tested for butyrylcholinesterase (BChE) activity and phenotype. The phenotype was measured as percent inhibition in the presence of dibucaine. It was found that the Iranian population had an extraordinarily high frequency of the atypical variant of butyrylcholinesterase. 70% to 80% of Iranians carried the atypical mutation (Asp70Gly) on one allele. This contrasts with European and American populations where only 4% carry the atypical allele. The atypical variant of butyrylcholinesterase is known to be associated with prolonged apnea after administration of the muscle relaxants succinylcholine and mivacurium, and is also thought to be associated with abnormal sensitivity to cocaine toxicity. This study demonstrates that the ethnic background of a person has an important role in a person's response to drugs.     

Inhibition of two different cholinesterases by tacrine

Kinetic parameters of the effect of tacrine as a cholinesterase inhibitor have been studied in two different sources: snake venom (Bungarus sindanus) acetylcholinesterase (AChE) and human serum butyrylcholinesterase (BChE). Tacrine inhibited both venom acetylcholinesterase (AChE) as well as human serum butyrylcholinesterase (BChE) in a concentration-dependent manner. Kinetic studies indicated that the nature of inhibition was mixed for both enzymes, i.e. Km values increase and Vmax decrease with the increase of the tacrine concentration. The calculated IC50 for snake venom and for human serum were 31 and 25.6 nM, respectively. Ki was observed to be 13 nM for venom acetylcholinesterase (AChE) and 12 nM for serum butyrylcholinesterase (BChE). KI (constant of AChE-ASCh-tacrine complex into AChE-ASCh complex and tacrine) was estimated to be 20 nM for venom and 10 nM for serum butyrylcholinesterase (BChE), while the gammaKm (dissociation constant of AChE-ASCh-tacrine complex into AChE-tacrine complex and ASCh) were 0.086 and 0.147 mM for snake venom AChE and serum BChE, respectively. The present results suggest that this therapeutic agent used for the treatment of Alzheimer's disease can also be considered an inhibitor of snake venom and human serum butyrylcholinesterase. Values of Ki and KI show that tacrine had more affinity with these enzymes as compared with other cholinesterases from the literature.     

The interaction of amiloride with acetylcholinesterase and butyrylcholinesterase

The diuretic drug amiloride was found to be a powerful inhibitor of the reaction of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with their specific choline ester substrates. The inhibition constant is in the micromolar range. On the other hand, when added to a mixture of cholinesterase (AChE and BChE) and neutral substrates, amiloride, in some cases, enhanced the reaction rate. The rate of the reaction of butyrylcholinesterase with p-nitrophenyl butyrate was increased up to 12 fold by amiloride.     

A versatile equation to describe reversible enzyme inhibition and activation kinetics: modeling beta-galactosidase and butyrylcholinesterase

Current treatments for Alzheimer's disease involve inhibiting cholinesterases. Conversely, cholinesterase stimulation may be deleterious. Homocysteine is a known risk factor for Alzheimer's and vascular diseases and its active metabolite, homocysteine thiolactone, stimulates butyrylcholinesterase. Considering the opposing effects on butyrylcholinesterase of homocysteine thiolactone and cholinesterase inhibitors, understanding how these molecules alter this enzyme may provide new insights in the management of dementia. Butyrylcholinesterase does not strictly adhere to Michaelis-Menten parameters since, at higher substrate concentrations, enzyme activation occurs. The substrate activation equation for butyrylcholinesterase does not describe the effects of inhibitors or non-substrate activators. To address this, global data fitting was used to generate a flexible equation based on Michaelis-Menten principles. This methodology was first tested to model complexities encountered in inhibition by imidazole of beta-galactosidase, an enzyme that obeys Michaelis-Menten kinetics. The resulting equation was sufficiently flexible to permit expansion for modeling activation or inhibition of butyrylcholinesterase, while accounting for substrate activation of this enzyme. This versatile equation suggests that both the inhibitor and non-substrate activator examined here have little effect on the substrate-activated form of butyrylcholinesterase. Given that butyrylcholinesterase inhibition can antagonize stimulation of this enzyme by homocysteine thiolactone, cholinesterase inhibition may have a role in treating Alzheimer and vascular diseases related to hyperhomocysteinemia.     

Spontaneous reactivation of phosphinylated human erythrocyte acetylcholinesterase and human serum butyrylcholinesterase

This report documents studies on the spontaneous reactivation of human erythrocyte acetylcholinesterase and human serum butyrylcholinesterase following inhibition by organophosphinate esters. The spontaneous reactivation reactions were carried out at 26.0 degrees C in 0.10 M phosphate buffer of pH 7.6. Based upon results at 24 h, human serum butyrylcholinesterase inhibited with 4-nitrophenyl methyl (4-methoxyphenyl) phosphinate was the most responsive (92.5% recovery) of the nine esters studied. Using the same criteria, the most active compound in the human erythrocyte acetylcholinesterase studies was 4-nitrophenyl methyl(phenyl)phosphinate (74.2% recovery). With seven of the nine compounds examined the response was greater from the serum enzyme than from the erythrocyte enzyme.     

A versatile equation to describe reversible enzyme inhibition and activation kinetics: Modeling β-galactosidase and butyrylcholinesterase

Current treatments for Alzheimer's disease involve inhibiting cholinesterases. Conversely, cholinesterase stimulation may be deleterious. Homocysteine is a known risk factor for Alzheimer's and vascular diseases and its active metabolite, homocysteine thiolactone, stimulates butyrylcholinesterase. Considering the opposing effects on butyrylcholinesterase of homocysteine thiolactone and cholinesterase inhibitors, understanding how these molecules alter this enzyme may provide new insights in the management of dementia. Butyrylcholinesterase does not strictly adhere to Michaelis–Menten parameters since, at higher substrate concentrations, enzyme activation occurs. The substrate activation equation for butyrylcholinesterase does not describe the effects of inhibitors or non-substrate activators. To address this, global data fitting was used to generate a flexible equation based on Michaelis–Menten principles. This methodology was first tested to model complexities encountered in inhibition by imidazole of β-galactosidase, an enzyme that obeys Michaelis–Menten kinetics. The resulting equation was sufficiently flexible to permit expansion for modeling activation or inhibition of butyrylcholinesterase, while accounting for substrate activation of this enzyme. This versatile equation suggests that both the inhibitor and non-substrate activator examined here have little effect on the substrate-activated form of butyrylcholinesterase. Given that butyrylcholinesterase inhibition can antagonize stimulation of this enzyme by homocysteine thiolactone, cholinesterase inhibition may have a role in treating Alzheimer and vascular diseases related to hyperhomocysteinemia.     

Selective reversible inhibition of human butyrylcholinesterase by aryl amide derivatives of phenothiazine

Evidence suggests that specific inhibition of butyrylcholinesterase may be an appropriate focus for the development of more effective drugs to treat dementias such as Alzheimer's disease. Butyrylcholinesterase is a co-regulator of cholinergic neurotransmission and its activity is increased in Alzheimer's disease, and is associated with all neuropathological lesions in this disease. Some selective butyrylcholinesterase inhibitors have already been reported to increase acetylcholine levels and to reduce the formation of abnormal amyloid found in Alzheimer's disease. Synthesized N-(10)-aryl and N-(10)-alkylaryl amides of phenothiazine are specific inhibitors of butyrylcholinesterase. In some cases, inhibition constants in the nanomolar range are achieved. Enzyme specificity and inhibitor potency of these molecules can be related to molecular volumes, steric and electronic factors. Computed logP values indicate high potential for these compounds to cross the blood-brain barrier. Use of such butyrylcholinesterase inhibitors could provide direct evidence for the importance of this enzyme in the normal nervous system and in Alzheimer's disease.     

Synthesis and structure-activity relationships of open D-Ring galanthamine analogues

Open D-ring galanthamine analogues were prepared using ring-opening reactions of the quaternarized urethane or oxazolidine functions and were evaluated for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition potency.