Acetylcholinesterase in mouse brain, erythrocytes and muscle

Statistical modeling-approach for optimization of Cu2+ biosorption by Azotobacter nigricans NEWG-1; characterization and application of immobilized cells for metal removal

Heavy metals are environmental pollutants affect the integrity and distribution of living organisms in the ecosystem and also humans across the food chain. The study targeted the removal of copper (Cu²⁺) from aqueous solutions, depending on the biosorption process. The bacterial candidate was identified using 16S rRNA sequencing and phylogenetic analysis, in addition to morphological and cultural properties as Azotobacter nigricans NEWG-1. The Box-Behnken design was applied to optimize copper removal by Azotobacter nigricans NEWG-1 and to study possible interactive effects between incubation periods, pH and initial CuSO₄ concentration. The data obtained showed that the maximum copper removal percentage of 80.56% was reached at run no. 12, under the conditions of 200 mg/L CuSO₄, 4 days’ incubation period, pH, 8.5. Whereas, the lowest Cu²⁺ removal (12.12%) was obtained at run no.1. Cells of Azotobacter nigricans NEWG-1 before and after copper biosorption were analyzed using FTIR, EDS and SEM. FTIR analysis indicates that several functional groups have participated in the biosorption of metal ions including hydroxyl, methylene, carbonyl, carboxylate groups. Moreover, the immobilized bacterial cells in sodium alginate-beads removed 82.35 ± 2.81% of copper from the aqueous solution, containing an initial concentration of 200 mg/L after 6 h. Azotobacter nigricans NEWG-1 proved to be an efficient biosorbent in the elimination of copper ions from environmental effluents, with advantages of feasibility, reliability and eco-friendly.

Biochemical adaptation in brain Acetylcholinesterase during acclimation to sub-lethal temperatures in the eurythermal fish Tilapia mossambica

Tilapia mossambica is a eurythermal tropical fish. We studied the effect of temperature on the kinetics of brain Acetylcholinesterase (AChE) during adaptation to sublethal temperatures by acclimating the fish to 37 °C, and controls to 25 °C. Electrophoresis showed the presence of two AChE bands that did not change in position or intensity with acclimation period or temperature. The apparent K_m was 0.23 ± 0.01 mM ATChI and remained relatively constant over the in vitro assay temperature range 10 °C to 40 °C. Biochemical characterization suggested that the enzyme is a ‘eurytolerant protein’ in its stability of kinetic and thermal properties over a wide temperature range. Thermal stability and arrhenius plots suggested that the AChE was made up of two forms that differed in their thermal properties.The two molecular forms of acetylcholinesterase were purified from the brain of T. mossambica. Molecular weight studies revealed that the two forms were size isomers: a monomer of 59 KDa and a tetramer of 244 KDa. They differed in their K_ms, thermal stabilities and energies of activation. We suggest that biochemical adaptation to temperature in the brain acetylcholinerase system of the fish Tilapia mossambica is based on the aggregation-dissociation of these size isomers.

Prevention of scopolamine-induced memory deficits by schisandrin B, an antioxidant lignan from Schisandra chinensis in mice

The preventive effect of schisandrin B (Sch B), an antioxidant ingredient of Schisandra chinensis, was studied on scopolamine-induced dementia in mouse. Scopolamine developed oxidative stress in the brain with the decreased levels of antioxidant enzymes and increased nitrite level. At the same time, a significant impairment of learning and memory occurred when evaluated by passive avoidance task (PAT) and Morris water maze (MWM) with concomitant increase of acetylcholinesterase (AChE) activity and decreased acetylcholine levels. Pre-treatment by Sch B (10, 25, 50 mg/kg) effectively prevented scopolamine-induced oxidative stress and improved behavioural tasks. Further, the scopolamine-induced increase in AChE activity was significantly suppressed and the level of acetylcholine was maintained as normal by Sch B treatment. These results suggest that Sch B have protective function against cerebral functional defects such as dementia not only by antioxidant prevention but also exerting its potent cognitive-enhancing activity through modulation of acetylcholine level.

Effect of Shengmai-san on cognitive performance and cerebral oxidative damage in BALB/c mice

The aim of this study was to examine the effect of Shengmai-san (SMS) on learning and memory impairment induced by scopolamine (1 mg/kg, i.p.) in mice. The passive avoidance task (PAT) and Morris water maze (MWM) test served as the behavioral models for testing memory. To elucidate the mechanism of its cognitive-enhancing activity, the effects of SMS (2, 4, or 8 g/kg) on activities of acetylcholinesterase (AChE) and antioxidant enzymes and levels of acetylcholine (ACh) and nitrite were evaluated in brain homogenate. Tacrine (THA) (10 mg/kg, p.o.) was used as a reference drug. SMS (4 or 8 g/kg) significantly prevented scopolamine-induced impairments as measured by the PAT and MWM (probe trial session). SMS (4 or 8 g/kg) also significantly reduced the oxidative-nitrative stress, as evidenced by decreased malondialdehyde and nitrite levels and by its prevention of decreases in glutathione and superoxide dismutase levels. The activity of AChE was decreased in scopolamine-treated mice but was inhibited significantly by SMS treatment (4 or 8 g/kg) in both salt- and detergent-soluble fractions of brain homogenates. Further SMS treatment (4 or 8 g/kg) significantly increased the ACh levels in the brain homogenate to a level similar to that observed in THA treatment. Thus, the significant cognitive enhancement observed after 7 days of administration of SMS is closely related to the strong antioxidant properties of SMS in addition to its inhibition of brain AChE activity. These findings stress the critical impact of SMS on higher brain functions such as learning and memory.

A comparative study in rodents of standardized extracts of Bacopa monniera and Ginkgo biloba: anticholinesterase and cognitive enhancing activities

Bacopa monniera and Ginkgo biloba are well-known cognitive enhancers in Indian and Chinese traditional medicine systems. Standardized extracts of B. monniera and G. biloba were used to evaluate the antidementic and anticholinesterase activities in adult male Swiss mice. Antidementic activity was tested against scopolamine (3 mg/kg ip)-induced deficits in passive avoidance test. Three different extracts of B. monniera (30 mg/kg) and extract of G. biloba (15, 30 and 60 mg/kg) were administered postoperatively, daily for 7 days and 60 min after the last dose, i.e., on Day 7, first trial was conducted. In passive avoidance test, increased transfer latency time (TLT) and no transfer response (NTR) were taken as criteria for learning. TLT and NTR were significantly increased and decreased in second trial, 24 h after the first trial in control group and scopolamine-dementia group, respectively. The B. monniera- and G. biloba-treated groups produced significant increase in TLT and NTR on second trial (40-80%) after scopolamine treatment, thus, attenuating its antidementic effect. Both the extracts showed a dose (10-1000 microg)-dependent inhibitory effect on acetylcholinesterase (AChE) activity (in vitro), performed spectrophotometrically. IC(50) of G. biloba was 268.33 microg, whereas none of the extracts of B. monniera showed more than 50% inhibition. At a dose concentration of 30 and 60 mg/kg, extracts of G. biloba showed a cognitive enhancing property and, at the same time, a significant decrease in AChE-specific activity in both per se and scopolamine-dementia groups. These extracts possess a significant anticholinesterase and antidementic properties, which may be useful in the treatment of dementia.

Effect of ovariectomy and estrogen supplementation on brain acetylcholinesterase activity and passive-avoidance learning in rats

The effect of ovariectomy and estrogen treatment on the brain acetylcholinesterase activity and cognition in rats was investigated in this study. Ovariectomized and nonovariectomized rats were treated subcutaneously with estradiol dipropionate for 8 d. In the single-trial, passive-avoidance test all the groups showed significant learning and retention of memory as evident by the increase in transfer latency time in trial 2 as compared with trial 1. No-transfer response was significantly increased in the estradiol-dipropionate-treated ovariectomized (80%) and nonovariectomized (60%) group as compared with the ovariectomized (30%) group. Specific activity of acetylcholinesterase was assayed spectrophotometrically in salt-soluble and detergent-soluble fractions of various brain areas: frontal cortex, cerebral cortex, striatum, hippocampus and hypothalamus, thalamus, pons, medulla, and cerebellum. The effect of ovariectomy and estradiol dipropionate was varied in both fractions of these brain areas. Estradiol dipropionate treatment could restore the acetylcholinesterase activity to the control level only in the detergent-soluble fraction of hypothalamus and salt-soluble fraction of hypothalamus, thalamus, and medulla in ovariectomized rats. The results indicate that ovariectomy alters acetylcholinesterase activity in the brain areas but not in a uniform manner and affects only qualitative aspects of cognitive function, which could be improved by estrogen supplementation.

Purification of soluble acetylcholinesterase from Japanese quail brain by affinity chromatography

The purification of a soluble acetylcholinesterase from Japanese quail brain using affinity chromatography on concanavalin A-Sepharose and edrophonium-Sepharose is described. The affinity matrix was synthesized by coupling an inhibitor edrophonium to epoxy-activated Sepharose. Acetylcholinesterase was purified 10,416-fold with a specific activity of 2500 U/mg protein. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol gave only one band with a molecular weight of 62.5 kDa. The molecular weight of the purified acetylcholinesterase was estimated to be 245.5 kDa by gel chromatography on Sephacryl S-200 under nondenaturing conditions. Based on the molecular weight obtained by both SDS-PAGE and gel filtration the purified acetylcholinesterase was assumed to be a tetrameric form.

Immobilization stress-induced changes in brain acetylcholinesterase activity and cognitive function in mice

In the present study, the effect of acute and chronic immobilization stress on brain acetylcholinesterase (AChE) enzyme activity and cognitive function in mice was investigated. Mice were immobilized by strapping for 150 min. One group of mice were only immobilized once (acute stress) while in another group mice were immobilized (150 min) daily for 5 consecutive days (chronic stress). Specific AChE enzyme activity (micromol min(-1)mg(-1)) was estimated by a spectrophotometric method in the whole brain of mice subjected to acute and chronic stress. In the acute stress group, AChE activity (0.24922 +/- 0.011) in the detergent-soluble fraction was found to be significantly decreased in comparison to the control group (0.33561 +/- 0.022). Chronic stress did not cause any significant change in AChE activity in the detergent-soluble fraction. In the salt-soluble fraction, AChE activity was significantly decreased only in the chronic stress group (0.08791 +/- 0.011) as compared to the control group (0.12051 +/- 0.011). A passive avoidance test was used to assess cognitive function. The transfer latency time (TLT) from a light to dark chamber was recorded in the control and acute stress groups (30 min after immobilization is over) on day 1 (Trial I) and the following day (Trial II). The acute stress group showed an increase (178%) in TLT from Trial I to Trial II, which was significantly higher than that of the non-stress control group (75%). In the chronic stress group, Trial I was undertaken 30 min after the last immobilization, i.e. on day 5 and 24 hr later, Trial II. However, the chronically stressed mice showed an increase (70%) in TLT similar to the control group. Thus this study shows that acute immobilization stress may enhance cognitive function in mice which may be attributed to a decrease in AChE activity leading to an increase in cholinergic activity in the brain.

Properties of acetylcholinesterase reconstituted in liposomes of a different charge

Acetylcholinesterase (AChE) purified from mouse brain was reconstituted in liposomes of a different charge, and the properties of liposome-associated AChE were investigated. Relative to the Km value (38.5 microM) of AChE bound to a neutral liposome, the value of AChE reconstituted in a negatively-charged liposome decreased to 23.3 microM, whereas that of AChE in a positively-charged liposome increased to 90.9 microM. Additionally, AChE bound to a positively-charged liposome expressed a wider range of optimum pH than the enzyme in a negatively-charged liposome. In a stability study, it was found that soluble AChE was unstable at pH 5.5 and 7.4, while it was relatively stable at pH 10. Noteworthy, the immobilization of AChE to liposome enhanced the stability of soluble enzyme at acidic and neutral pH. Moreover, in the stabilization of the enzyme, a neutral liposome was more effective than charged liposomes, of which a positively-charged liposome was more effective than a negatively-charged liposome at acidic pH. Based on these results, it is proposed that while the Km value and the pH dependence of AChE activity are affected by the charge of liposome, the stability of AChE is determined mainly by a hydrophobic binding to a phospholipid membrane.

Production and characterization of separate monoclonal antibodies to human brain and erythrocyte acetylcholinesterases

Four murine monoclonal antibodies (MAbs) of the IgM class were raised against human acetylcholinesterase (AChE; Ec 3.1.1.7). The MAbs BMS-3E4, BMS-7G10, and BMS-9F4 all recognized human erythrocyte AChE, while BMS-6D6 bound specifically to human soluble brain AChE, on the basis of immunobinding assays. Dose-response studies gave an ELISA ED50 titer of 4.5 x 10(-4) M for BMS-6D6, while BMS-3E4 gave the best titer at 8.8 x 10(-4) M. Sucrose density gradients demonstrated sedimentation of antigen-antibody complexes, consistent with earlier findings (i.e., BMS-6D6 bound with brain AChE while BMS-3E4 preferred erythrocyte (AChE). No cross-reactivity between the two MAbs against the two antigens was noted.

Potentiation effect of choline esters on choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase

The choline esters potentiated the choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase in proportion to the length of acyl group, although esters containing an acyl chain longer than the hexanoyl group exhibited a corresponding decrease in the potentiation. In structural requirement analysis it was found that both the quaternary ammonium moiety and the ester bond were important for the effective acceleration of choline-catalysed decarbamoylation. In general, the respective thiocholine ester was found to be more effective than the corresponding choline ester. Whereas the binding affinity (Ka) of choline in the decarbamoylation was not significantly altered, the maximum decarbamoylation rate (kr(max.)) of choline was greatly enhanced in the presence of choline esters or thiocholine esters. Along with the above observation, the isotope solvent effect, the effect of ionic strength and the antagonism studies demonstrate that the choline esters or thiocholine esters may interact with one of peripheral anionic sites, and thereby make the choline-catalysed decarbamoylation more favourable.

Effect of choline esters on the decarbamylation of dimethylcarbamyl-acetylcholinesterase

Acetylcholine and butyrylcholine exhibited the dose-dependent decarbamylation up to 0.2 mM, although at higher concentrations the decarbamylation degree declined. In combination with choline, butyrylcholine potentiated the choline-catalyzed decarbamylation by 30-100%, and was found to be more effective than acetylcholine in enhancing the decarbamylation. In kinetic analysis, it was observed that Ka value of choline was not remarkably altered by butyrylcholine whereas the maximum rate for decarbamylation was enhanced significantly in the presence of butyrylcholine, suggesting that butyrylcholine may affect the decarbamylation by interacting with the peripheral sites, different from the central active site which choline is known to interact with. In support of the suggestion, butyrylcholine was observed to compete with gallamine, a well known peripheral activator, and the effect of butyrylcholine was enhanced by three times at low ionic strength. In addition, acetylcholinesterase from mouse brain or bovine erythrocyte seemed to differ from electric eel enzyme in the interaction with butyrylcholine.

Establishment of megakaryoblastic cell lines by coinfection of Abelson murine leukemia virus and recombinant SV40-retrovirus

Murine embryonic cells including yolk sac prepared from 8-day embryos were co-infected with Abelson murine leukemia virus (A-MuLV) and/or a recombinant retrovirus containing large T and small t antigens, and early region of simian virus 40 (M-SV40). By coinfection with A-MuLV and M-SV40, megakaryoblastic cells were obtained in addition to mast cells and fibroblastic cells. However, following infection with A-MuLV or M-SV40 alone, no megakaryoblastic cells were detected, although mast cells and/or fibroblastic cells developed. The same results were obtained in several experiments. By single-cell transfer, 6 acetyl-cholinesterase (AchE)-positive clonal cell lines were established. Characteristics of megakaryocytes, such as AchE, glycoproteins IIb and IIIa, and platelet peroxidase were detected in two representative cells (C1 and C8). More significant changes expressing differentiation were observed following treatment with phorbol myristate acetate or pokeweed mitogen-stimulated murine spleen cell conditioned medium, although release of platelets was not observed. This is the first report showing development of megakaryocytic cells as the result of coinfection with retroviruses.

A comparison of the localization of acetylcholinesterase in the rat brain as demonstrated by enzyme histochemistry and immunohistochemistry

The localization of acetylcholinesterase (AChE) as revealed either by enzyme-histochemical or by immunohistochemical methods was compared in distinct regions of the rat brain. In general, the localization of AChE observed was nearly the same, whether revealed by histochemical demonstration of its catalytic activity or by immunohistochemical detection of the enzyme molecule itself, in all regions investigated. Penetration problems of the antibodies, however, arose on strong myelin sheaths of the facial nerve, for instance, where no immunohistochemical staining was found though there was a relatively strong histochemical reaction. These problems could be partly solved by increasing the normal concentration of Triton X-100 added to the immunohistochemical solutions (0.1%) to 2.5%. Furthermore, it seems that sites containing low amounts of AChE could be better detected by the enzyme-histochemical method, whereas the depiction of structures (particularly of nerve fibres) was somewhat sharper with the immunohistochemical method.

Acetylcholinesterase of Schistosoma mansoni: purification and characterization

Larval acetylcholinesterase (acetylcholine acetylhydrolase) EC 3.1.3.7 of the trematode Schistosoma mansoni was characterized and purified by affinity chromatography. The enzyme was solubilized from sonicated cercarial tissue and showed a Km value of 1.83 mM and a Vmax value of 102 U/mg protein. It was characterized as a true AChE since it hydrolyses acetylthiocholine more than seven times faster than butyrylthiocholine, and since it was inhibited by high concentrations of substrate. The enzyme was purified by affinity chromatography on a Sepharose column of the inhibitor [N-(6-aminocaproyl-6-aminocaproyl)-m-aminophenyl] trimethyl ammonium. The purified enzyme eluted from the column by decamethonium bromide migrated as a single band of 500 kD on nondenaturing polyacrylamide gel electrophoresis (PAGE), whether stained for proteins or for enzymatic activity. Analysis by SDS-PAGE revealed two major polypeptide bands of 76 kD and 30 kD. By labeling the enzyme with 3H-DFP (di-isopropyl-fluorophosphate), the 30-kD polypeptide was shown to contain the active site of the enzyme, with an additional labeled band of 110 kD also being detected. On the basis of our data we suggest that the principal species of S. mansoni AChE is a tetramer of four subunit polypeptides each of MW ca. 110 kD which are not linked by disulfide bonds, and which are further cleaved into two fragments, one of MW 76,000 and one of MW 30,000, the latter bears the active site.

Monoclonal antibodies to rat brain acetylcholinesterase: comparative affinity for soluble and membrane-associated enzyme and for enzyme from different vertebrate species

Seven unique monoclonal antibodies were generated to rat brain acetylcholinesterase. Upon density gradient ultracentrifugation, immunoglobulin complexes with the monomeric enzyme appeared as single peaks of acetylcholinesterase activity with a sedimentation coefficient approximately 3S greater than that of the free enzyme. This behavior is consistent with the assumption of one binding site per enzyme molecule. Apparent dissociation constants of these antibodies for rat brain acetylcholinesterase calculated on the basis of this assumption ranged from about 10 nM to more than 1,000 nM. Some of the antibodies were less able to bind the membrane-associated enzyme that required detergent for solubilization than the naturally soluble acetylcholinesterase of detergent-free brain extracts. Species cross-reactivity was investigated with crude brain extracts from mammals (human, mouse, rabbit, guinea pig, cow, and cat) and from other vertebrates (chicken, frog, and electric eel). Three antibodies bound rat acetylcholinesterase exclusively; one had nearly the same affinity for all mammalian acetylcholinesterases investigated; the remaining three showed irregular binding patterns. None of the antibodies recognized frog and electric eel enzyme. Pooled antibody was found to be suitable for specific immunofluorescence staining of large neurons in the ventral horn of the rat spinal cord and smaller cells in the caudate nucleus. Other potential applications of these antibodies are discussed.

Monoclonal antibodies to rabbit brain acetylcholinesterase: selective enzyme inhibition, differential affinity for enzyme forms, and cross-reactivity with other mammalian cholinesterases

Eleven unique monoclonal IgG antibodies were raised against rabbit brain acetylcholinesterase (AChE, EC 3.1.1.7), purified to electrophoretic homogeneity by a two-step procedure involving immunoaffinity chromatography. The apparent dissociation constants of these antibodies for rabbit AChE ranged from about 10 nM to more than 100 nM (assuming one binding site per catalytic subunit). Species cross-reactivity was investigated with crude brain extracts from rabbit, rat, mouse cat, guinea pig, and human. One antibody bound rabbit AChE exclusively; most bound AChE from three or four species; two bound enzyme from all species tested. Identical, moderate affinity for rat and mouse brain AChE was displayed by two antibodies; two others were able to distinguish between these similar antigens. Nine of the antibodies had lowered affinity for AChE in the presence of 1 M NaCl, but two were salt resistant. Analysis of mutual interferences in AChE binding suggested that certain of the antibodies were competing for nearby epitopes on the AChE surface. One antibody was a potent AChE inhibitor (IC50 = 10(-8) M), blocking up to 90% of the enzyme activity. Most of the antibodies were less able to bind the readily soluble AChE of detergent-free brain extracts than the AChE which required detergent for solubilization. The extreme case, an antibody that was unable to recognize nearly half of the "soluble" AChE, was suspected of lacking affinity for the hydrophilic enzyme form.

Two-step immunoaffinity purification of acetylcholinesterase from rabbit brain

Acetylcholinesterase (AChE; EC 3.1.1.7) extracted in 1% Triton X-100 from rabbit brain was purified 2,000-fold by chromatography on agarose conjugated with a monoclonal antibody directed against human red blood cell cholinesterase. After elution from the immunoadsorbent with pH 11 buffer, the preparation was purified further by affinity chromatography on phenyltrimethylammonium-Sepharose 4B with decamethonium elution. Overall yield of purified enzyme was 37% of the AChE originally solubilized, with a specific activity of 2,950 units/mg protein. Electrophoresis under reducing conditions in 7.5% sodium dodecyl sulfate polyacrylamide gels revealed only one silver-staining polypeptide band. A streamlined purification procedure enabled the isolation of electrophoretically homogeneous AChE to be completed in fewer than 7 days, at yields exceeding 50%. Electrophoretic analysis of purified AChE indicated an apparent MW of 71,000 for the monomeric subunit. Gel filtration and sucrose density gradient centrifugation in the presence of Triton X-100 showed little difference between the properties of the native and the purified enzyme. The molecular mass of the main species was estimated from the gel filtration and sedimentation data to be 280,000 daltons. Kinetic parameters of the purified protein (Km = 0.16 +/- 0.01 mM) were close to those of the native enzyme (Km = 0.12 +/- 0.01 mM) when examined with acetylthiocholine iodide as substrate. The two-step immunopurification procedure presented in this communication offers a convenient route to homogeneous neural AChE in quantities useful for detailed biochemical and immunochemical study.

An immunological study of rat acetylcholinesterase: comparison with acetylcholinesterases from other vertebrates

We have examined the immunoreactivity of acetylcholinesterase from different vertebrate species with a rabbit antiserum raised against the purified rat brain hydrophobic enzyme (G4 form). We found no significant interaction with enzymes from Electrophorus, Torpedo, chicken, and rabbit. The antiserum reacted with acetylcholinesterases from the brains of the other mammalian species studied, with titers decreasing in the following order: rat = mouse greater than human greater than bovine. The serum was inhibitory with murine and human acetylcholinesterases, but not with the bovine enzyme. The inhibition was partially depressed in the presence of salt (e.g., 1 M NaCl). In those species whose acetylcholinesterase was recognized by the antiserum, both soluble and detergent-soluble fractions behaved in essentially the same manner, interacting with the same antibodies. The apparent immunoprecipitation titer was decreased in the presence of salt, and it did not make any difference whether NaCl was included in the solubilization procedure or added to the extracts. Both G1 and G4 forms of acetylcholinesterase in the soluble and detergent-soluble fractions were recognized by the antiserum, and in the case of the human enzyme, by monoclonal antibodies produced against human erythrocyte acetylcholinesterase. However, the monomer G1 showed a clear tendency to form smaller complexes and precipitate less readily than the tetramer G4. Although we cannot exclude the existence of significant differences between the various molecular forms of acetylcholinesterase, our results are consistent with the hypothesis that they all derive from the same gene or set of genes by posttranslational modifications.

Characterization of acetylcholinesterase molecular forms in slow and fast muscle of rat

Multiple molecular forms of acetylcholinesterase (AChE EC 3.1.1.7) from fast and slow muscle of rat were examined by velocity sedimentation. The fast extensor digitorum longus muscle (EDL) hydrolyzed acetylcholine at a rate of 110 mumol/g wet weight/hr and possessed three molecular forms with apparent sedimentation coefficients of 4S, 10S, and 16S which contribute about 50, 35, and 15% of the AChE activity. The slow soleus muscle hydrolyzed acetylcholine at a rate of 55 mumol/g wet weight/hr and has a 4S, 10S, 12S, and 16S form which contribute 22, 18, 34, and 26% of AChE activity, respectively. A single band of AChE activity was observed when a 1M NaCl extract with CsCl (0.38 g/ml) was centrifuged to equilibrium. Peak AChE activity from EDL and SOL extracts were found at 1.29 g/ml. Resedimentation of peak activity from CsCl gradients resulted in all molecular forms previously found in both muscles. Addition of a protease inhibitor phenylmethylsulfonyl chloride did not change the pattern of distribution. The 4S form of both muscles was extracted with low ionic strength buffer while the 10S, 12S, and 16S forms required high ionic strength and detergent for efficient solubilization. All molecular forms of both muscles have an apparent Km of 2 x 10(-4) M, showed substrate inhibition, and were inhibited by BW284C51, a specific inhibitor of AChE. The difference between these muscles in regards to their AChE activity, as well as in the proportional distribution of molecular forms, may be correlated with sites of localization and differences in the contractile activity of these muscles.

An amphiphile-dependent form of human brain caudate nucleus acetylcholinesterase: purification and properties

Different forms of acetylcholinesterase (AChE), EC 3.1.1.7, were demonstrated in human brain caudate nucleus. One form was solubilized at high ionic strength, the other with Triton X-100. The detergent-extractable form was purified to homogeneity by affinity chromatography. This form of AChE is amphiphile-dependent; i.e., it was active only in the presence of amphiphiles (detergents or lipids). Further, the enzyme was shown to bind detergents and to interact hydrophobically with Phenyl-Sepharose. In the presence of detergents the enzyme is a tetramer (subunit molecular weight, 78,000) which aggregates on the removal of detergents. Human brain AChE showed a reaction of identity with human erythrocyte AChE in crossed-line immunoelectrophoresis. The high-salt-soluble brain enzyme did not cross-react with the erythrocyte enzyme. The two classes of AChE seem not to be related, as they show no common antigenic determinant.

Acetylcholinesterase molecular forms from rat and human erythrocyte membrane

1. Some of the biochemical characteristics of acetylcholinesterase from rat and human erythrocytes were studied. 2. Both for rat and man two different acetylcholinesterase molecular forms were identified by gel electrophoresis. The faster moving form is less conspicuous and is not present in all individuals, therefore single-banded and double-banded preparations of red cell acetylcholinesterase can be obtained. The two components appear to be isomers of different molecular size (approximately Mr 150 000 and Mr 245 000) as estimated by gel electrophoresis at different polyacrylamide concentrations. 3. A single band, with a molecular weight of approximately 135 000, was obtained by sodium dodecyl sulphate gel electrophoresis. These results suggest that the faster moving form is a protomer and the slower a dimer. 4. The different sedimentation values obtained by density gradient centrifugation in the presence of Triton X-100 of double-banded (5.3S) and single-banded (6.3S) rat and human acetylcholinesterase preparations, are consistent with a protomer-dimer hypothesis. 5. The isoelectric pattern observed for both double- and single-banded preparations was similar for rat and man acetylcholinesterase and showed a considerable microheterogeneity (thirteen activity bands for rat and eleven for man with isoelectric values from 4.6 to 5.9).

Potentiation of the carotid artery occlusion reflex by a cholinergic system in the posterior hypothalamic nucleus

Bilateral occlusion of the common carotid arteries of urethane-anesthetized rats evoked a pressor response of 14 +/- 1 mm Hg. Injection into the lateral cerebral ventricle of neostigmine (0.2-1.0 microgram) or physostigmine (10-15 microgram) caused a dose-dependent increase in basal blood pressure and in the magnitude of the carotid artery occlusion (CAO) pressor reflex. Neostigmine (1 microgram) and physostigmine (15 microgram) caused nearly maximal and approximately equal degrees of cholinesterase inhibition in several brain regions. The recovery of the cardiovascular parameters and of brain cholinesterase activity was significantly faster following physostigmine compared to neostigmine. Prior intracerebroventricular injection of atropine (0.3 microgram) or hemicholinium-3 (20 microgram) prevented the increases in basal pressure and the CAO pressor response. Potentiation of the CAO reflex also followed injection of physostigmine or neostigmine into the posterior hypothalamic nucleus and of injection of physostigmine intravenously. Injection of atropine bilaterally into ther posterior hypothalamic nucleus prior to intravenous injection of physostigmine prevented the potentiation of the CAO reflex but not the increase in basal blood pressure. These results indicate that acetylcholine in the posterior hypothalamic nucleus serves as a neurotransmitter in a pathway which can potentiate the pressor response to carotid artery occlusion and thus modulate baroreceptor reflexes.

The aryl acylamidases and their relationship to cholinesterases in human serum, erythrocyte and liver

Human serum aryl acylamidase associated with serum cholinesterase was purified to homogeneity. Evidence for the identity of the two enzymes was based on co-elution profiles, co-purification in the different steps including affinity chromatography with constant ratios of specific activity and percentage recoveries, co-migration on gel electrophoresis, parallel inhibition by typical cholinesterase inhibitors and co-precipitation by antibody raised against the purified enzyme. Human liver aryl acylamidase was partially purified. Based on the elution profiles, purification data, inhibitory characteristics and gel electrophoresis it was concluded that aryl acrylamidase of liver was not associated with liver cholinesterase. More conclusive evidence for the non-association of the liver aryl acylamidase and cholinesterase came from their clear-cut separation on procainamide-Sepharose affinity chromatography. Both the serum and liver aryl acylamidase were compared with the purified erythrocyte aryl acylamidase associated with acetylcholinesterase. While the erythrocyte and serum aryl acylamidases showed some similarities in their sensitivities to amines like serotonin or tryptamine and choline derivatives, the liver enzyme was unaffected by any of these compounds. A notable observation was the activation by tyramine of the serum aryl acylamidase but not the erythrocyte and liver aryl acylamidases. The liver aryl acylamidase also differed from the other two in its relative insensitivity to inhibition by eserine, neostygmine and other cholinesterase inhibitors. Immunodiffusion and immunoprecipitation studies showed that the aryl acylamidases from the liver and erythrocytes were immunologically non-identical with the serum enzyme.

Affinity chromatography of acetylcholinesterase. The use of Amberlite CG-120 for dissociating the enzyme-inhibitor complex

Acetylcholinesterase from rat brain was solubilized with 1% (w/v) Triton X-100 and purified by affinity chromatography. Two different ligands were investigated. The most efficient purification was obtained when the enzyme was eluted from a column containing the acetylcholinesterase inhibitor N-methyl-3-aminopyridinium iodide covalently linked to Sepharose 2B. An initial recovery of 6% of the applied enzyme increased to 70% after treatment with Amberlite CG-120. The partially purified enzyme had a specific activity of 205 mumoles min-1 mg-1 and a purification of 162-fold with respect to the brain homogenate and 44-fold with respect to the Triton solubilized enzyme. The effect of metal cations on the stability of the partially purified enzyme during storage at --20 degrees C was also investigated. The addition of MgCl2 to the purified enzyme prevented the rapid loss of enzyme activity.

Neurotransmitter metabolizing enzymes and plasma butyrylcholinesterase in mice exposed to trichloroethylene

Acetylcholinesterase, glutamine synthetase, acid phosphatase and glutamate dehydrogenase activity in brain and cholinesterase activity in blood were investigated in mice exposed to 170 p.p.m. trichloroethylene (TCE) during 30 days. The neuronal enzymes remained unaffected which suggests that no general damage occurred to either the glia or the nerve cell populations. In accordance with this no effect was seen on acid phosphatase. In contrast, plasma butyrylcholinesterase increased twofold in exposed male mice while it was unaffected in females. Liver weight in males and females increased with a factor of 1.5 and 1.9, respectively.

Altered acetylcholinesterase isozyme patterns in mice with hereditary muscular dystrophy

Normal and dystrophic mouse muscles were separated into a predominantly white muscle fraction (gastrocnemius, extensor digitorum longus) and a predominantly red muscle fraction (diaphragm). Acetylcholinesterase (AChE) was extracted from each muscle fraction using a Triton X-100/NaCl buffer. Six forms of AChE were separated from each muscle homogenate by velocity sedimentation on linear sucrose gradients. Their apparent sedimentation coefficients in each case were 19.7S, 16.0S, 13.3S, 10.4S, 7.6S, and 3.9S. Gel electrophoresis of crude muscle homogenates under nondenaturing conditions (native gels) and of ech separate isozyme fraction gave one band of AChE activity with a consistent Rf (relative mobility) value. Reelectrophoresis of native gel bands on SDS/acrylamide slab gels revealed a similar monomeric subunit protein from either crude muscle homogenates or isozyme fractions with an apparent molecular weight of approximately 69,000 daltons. Our results indicate that the AChE distribution and activity are severely affected in dystrophic "white" muscles (anaerobic) but much less so in "red" muscles (aerobic). Dystrophic predominantly white muscles weigh less, contain less protein, and have a decreased total AChE activity in comparison with their normal counterparts. Furthermore, the relative proportions of AChE activity in each isozyme fraction is altered between normal white and dystrophic white muscle fractions: i.e., dystrophic white muscle contains a decreased proportion of a low molecular weight form (7.6S) and increased proportions of higher molecular weight forms (16.0S, 19.7S). In contrast, no significant differences occur in AChE activity or distribution between normal and dystrophic predominantly red muscle. The changes in white muscle AChE are toward a pattern common to red muscle. This suggests that the effect of muscular dystrophy and its related stress on mouse white muscle is at least in part a shift from a predominantly anaerobic, fatigable metabolism to an aerobic, fatigue-resistant metabolism.

Purification and characterization of an ascidian larval acerylcholinesterase

Larval acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) of the ascidian Ciona intestinalis (L.) was purified by a two-step affinity chromatography procedure. Concavanalin A-Sepharose chromatography in batches provided the initial purification and was followed by chromatography on columns to which competitive inhibitors of acetylcholinesterase had been attached. The most efficient of these used m-carboxyphenylmethylammonium iodide coupled to Sepharose 4B via a hydrophobic 6-carbon spacer. In combination with the concanavalin A-Sepharose step, this affinity resin yielded recoveries of 30-39% with specific activities ranging from 580-730 units/mg protein, a total purification of 5000-7000-fold. Analysis of this product by polycrylamide gel electrophoresis in the presence of SDS and beta-mercaptoethanol revealed a single major polypeptide of M(r) 65 000-70 000. This protein was identified as the basic catalytic subunit of acetylcholinesterase by its coelectrophoresis with [(3)H]diisopropyl fluorophosphate-labeled enzyme. Sucrose density gradient studies demonstrated that the purified enzyme consisted of three distinct species that appeared to be qualitatively the same as those seen in crude extracts. The largest species (11 S) is possibly a tetramer of the basic catalytic subunit and the two smaller forms, the monomer and dimer. Purified enzyme was also used to produce anti-acetylcholinesterase antibody in rabbits. IgG prepared from the sera of immunized rabbits was shown to react completely (greater than 98%) with acetylcholinesterase from crude larval homogenates. This result also supports the conclusions that no qualitative selection occurred during the purification procedure and that the basic catalytic subunit is a fundamental component of all the larval acetylcholinesterases.

The identity of the serotonin-sensitive aryl acylamidase with acetylcholinesterase from human erythrocytes, sheep basal ganglia and electric eel

The identity of the serotonin-sensitive aryl acylamidase with acetylcholinesterase from three diverse sources, namely sheep basal ganglia, human erythrocyte membrane and electric eel, was examined. Both the enzymes co-purified with constant ratios of specific activity from all the three sources by different affinity chromatographic techniques. The ratio of acetylcholinesterase to aryl acylamidase activity was highest for basal ganglia, less for erythrocyte and lowest for eel enzymes. Both the purified enzymes co-migrated on polyacrylamide gel electrophoresis either as a single species or multiple species under different conditions. Gel density gradient electrophoresis indicated identical migration rates of both the enzymes. Extraction of the enzymes from the three sources by different techniques of membrane disruption and subsequent gel filtration on Sepharose 6B showed multiple peaks of enzyme activity. Both the enzymes had identical elution profiles on Sepharose 6B gel filtration. All the enzyme peaks from Sepharose 6B on gel electrophoresis showed co-migration of the enzyme activities. Apart from inhibition by serotonin and acetylcholine the purified aryl acylamidases from all the three sources were potently inhibited by neostygmine, eserine and BW 284C51, all strong inhibitors of acetylcholinesterase. It is suggested that the serotonin-sensitive aryl acylamidase is identical with acetylcholinesterase.

The multiple forms of brain acetycholinesterase. III. Implications for the histochemical demonstration of acetylcholinesterase

The multiple forms of acetylcholinesterase (AChE, E.C. 3.1.1.7) have been investigated with regard to their histochemical demonstrability. Their pattern is influenced by buffer treatment, fixation, and by incubation conditions causing aggregation and disaggregation as well as loss or inactivation of individual forms. The standard histochemical method for AChE preferentially demonstrates the high molecular forms. Most of the oligomer forms are washed out or inactivated. A selective demonstration of the highly aggregated forms is possible either by inhibition of the oligomers with diisopropylfluoridate (DFP) or by specifically dissolving them out. No reason could be found for the selective demonstration of the low molecular weight forms.

Acetylcholinesterase: a probe for the study of antiarrhythmic drug-membrane interactions

Structural consequences of antiarrhythmic drug interaction with erythrocyte membranes were analyzed in terms of resulting changes in the activity of membrane-associated acetylcholinesterase. When enzyme inhibitory effects of drugs were compared at concentrations producing an equivalent degree of erythrocyte antihemolysis, a number of distinct groupings emerged, indicating that the molecular consequences of drug-membrane interaction are not identical for all agents examined. Differences in drug-induced acetylcholinesterase inhibition in intact erythrocytes, erythrocyte membranes and a brain synaptic membrane preparation emphaized the role of membrane structural organization in determining the functional consequences of antiarrhythmic interaction in any given system. While the inhibitory actions of lidocaine, D-600 and bretylium in intact red cells were not altered by an increased transmembrane chloride gradient, enhanced enzyme inhibition by quinidine and propranolol was observed under these conditions. The diverse perturbational actions of these membrane-stabilizing antiarrhythmics observed here may be indicative of a corresponding degree of complexity in the mechanisms whereby substances modify the potential-dependent properties of excitable tissues.