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PubMed1995

Human biliary epithelial cell line Mz-ChA-1 expresses new isoforms of calmodulin-dependent protein kinase II.

BACKGROUND & AIMS: Calmodulin-dependent protein kinase II is a family of closely related multimeric enzymes that regulate a wide variety of cellular processes. In biliary epithelial cells, this kinase seems to regulate Ca(2+)-dependent CI- currents. The aim of this study was to identify isoforms of this kinase expressed in biliary cells. METHODS: Sequencing of reverse-transcription polymerase chain reaction products identified multiple isoforms in Mz-ChA-1 cells. RESULTS: Two previously identified isoforms (gamma B and gamma C) and three new isoforms (gamma D, gamma E, and gamma F) of calmodulin-dependent protein kinase II were identified. Each of the novel isoforms contains a unique insert of 114 base pairs in the association region. This insert lies outside the previously identified variable region. In addition, gamma D and gamma F contained other deletions (42 and 69 base pairs, respectively) in the variable region. These isoforms are expressed in a variety of tissues, including biliary epithelial and gallbladder cells, but only gamma C is expressed in rat hepatocytes. CONCLUSIONS: Identification of these biliary kinase isoforms paves the way for future studies that will elucidate the role of individual isozymes in agonist-stimulated biliary Cl- and fluid secretion.

Amino Acid Sequence↗
PubMed1992

Isoform purification of gastric lipases. Towards crystallization.

Several isoforms of rabbit and human gastric lipases have been purified. These isoforms have the same apparent molecular weight (Mr approximately 50,000), but very different isoelectric points. Some of these isoforms were purified: pI 7.2 and 6.5 in the case of rabbit gastric lipase; and pI 7.4 and 7.2 in that of human gastric lipase. All the purified isoforms were found to have the same specific lipase activity (around 1200 units per mg of protein, measured on tributyrin as substrate). The isoforms of dog gastric lipase are more closely related, and could not be separated. Partial enzymatic deglycosylation of human gastric lipase reduced the apparent molecular weight from Mr approximately 50,000 to Mr approximately 43,000 and induced a change in the isoelectrofocusing pattern and the emergence of a new isoform (pI 7.3). It is concluded that the charge heterogeneity of gastric lipases is at least partly due to the glycan moiety of the molecule, which amounts to approximately 14% of the total molecular weight. Several crystallization trials on purified native preparations of rabbit and human gastric lipases were unsuccessful, whereas crystals were obtained from native dog gastric lipase and all the purified isoforms of rabbit and human gastric lipases, some of which were crystallographically characterized.

Animals↗
PubMed1990

Werdnig-Hoffmann disease: myosin isoform expression not arrested at prenatal stage of development.

It has been suggested, on the basis of mostly morphological and some biochemical evidence, that defective innervation of muscle of patients with Werdnig-Hoffmann (WH) disease results in maturational arrest of the fibers at a stage comparable to 20-week gestational muscle. Therefore, with the use of recently developed and characterized, myosin-isoform-specific monoclonal antibodies (McAbs), an immunocytochemical study of muscle of 6 children with Werdnig-Hoffmann disease was done to determine if the pattern of expression of myosin heavy chain isoforms (MHC) in these fibers was similar to that of 20-week gestation muscle. This work showed that the MHC isoform expression in the muscle of the children with WH did not mimic that seen in 20-week gestation muscle since only a few fibers (less than 1-11%) in each specimen expressed prenatal MHC as detected by reactivity to McAb, ALD 180 (specific for a prenatal MHC) whereas virtually all of the fibers from 20-week gestation muscle were strongly reactive with ALD 180. The majority of the fibers expressed either adult fast MHC or adult slow MHC similar to that seen in normal muscle, although some co-expressed multiple MHC isoforms. Our results indicate that the difference of adult MHC isoforms in the muscle fibers of WH patients either proceeds in the absence of innervation or that denervation of muscle fibers is subsequent to the neural input required to initiate myosin isoform transitions to the adult isoforms.

Antibodies, Monoclonal↗
PubMed1982

alpha 1-Antitrypsin microheterogeneity. Isolation and physiological significance of isoforms.

alpha 1-Antitrypsin has a microheterogeneity evident on isoelectric focusing as three major and several minor bands. We have identified the carbohydrate structures of the major bands; band 6 (isoform I) has three bi-antennary sidechains, band 4 (isoform II) has two bi- and one tri-antennary and band 2 (isoform III) has one bi- and two tri-antennary sidechains. The identity of the isoforms with the bands permitted their measurement in plasma by photometric scanning of the electrofocused gels. In healthy controls the levels of isoforms I, II and III were relatively constant and in the proportions of 5, 4 and 1, respectively. A marked change occurred during inflammation and oestrogen stress with isoforms II and III accounting for most of the increase in alpha 1-antitrypsin. One possible consequence of the changed proportions was shown to be the increased catabolism of the partially desialylated tri-antennary isoforms compared to that of the predominant bi-antennary form of the healthy individual.

Animals↗
PubMed1992

Phosphorylation of the cardiac isoform of calsequestrin in cultured rat myotubes and rat skeletal muscle.

Calsequestrin is a high-capacity Ca(2+)-binding protein and a major constituent of the sarcoplasmic reticulum (SR) of both skeletal and cardiac muscle. Two isoforms of calsequestrin, cardiac and skeletal muscle forms, have been described which are products of separate genes. Purified forms of the two prototypical calsequestrin isoforms, dog cardiac and rabbit fast-twitch skeletal muscle calsequestrins, serve as excellent substrates for casein kinase II and are phosphorylated on distinct sites (Cala, S.E. and Jones, L.R. (1991) J. Biol. Chem 266, 391-398). Dog cardiac calsequestrin is phosphorylated at a 50 to 100-fold greater rate than is rabbit skeletal muscle calsequestrin, and only the dog cardiac isoform contains endogenous Pi on casein kinase II phosphorylation sites. In this study, we identified and examined both calsequestrin isoforms in rat muscle cultures and homogenates to demonstrate that the cardiac isoform of calsequestrin in rat skeletal muscle was phosphorylated in vivo on sites which are phosphorylated by casein kinase II in vitro. Phosphorylation of rat skeletal muscle calsequestrin was not detected. In tissue homogenates, cardiac and skeletal muscle calsequestrin isoforms were both found to be prominent substrates for endogenous casein kinase II activity with cardiac calsequestrin the preferred substrate. In addition, these studies revealed that the cardiac isoform of calsequestrin was the predominant form expressed in skeletal muscle of fetal rats and cultured myotubes.

Animals↗
PubMed1993

Characterization of Serratia marcescens nuclease isoforms by plasma desorption mass spectrometry.

Isoforms of Serratia marcescens nuclease found in the natural nuclease produced by S. marcescens and in recombinant nuclease produced by Escherichia coli were structurally characterized by peptide mapping using plasma desorption mass spectrometry. The nuclease isoforms produced and secreted from S. marcescens B10M1, which are present in much greater amounts than in S. marcescens W225 nuclease produced by E. coli, were characterized completely and the information used to facilitate characterization of the recombinant nuclease isoforms. After purification of the nuclease the isoforms were separated on a DEAE-cellulose anion-exchange column and then digested with endoproteinase Lys-C. The peptides generated were isolated by reverse-phase HPLC and their molecular masses determined by plasma desorption mass spectrometry. Comparison of the peptides from the native nuclease, Sm2, and the two isoforms, Sm1 and Sm3, revealed that they differed only in the N-terminus, the latter being found to lack three amino acids in Sm1 and one amino acid in Sm3. No interior post-translational changes were found in either of the three isoforms. Using this information we were able to confirm that Sm1, the isoform lacking three amino acids, was also present in very small amounts in recombinant S. marcescens W225 nuclease produced and excreted by E. coli.

Amino Acid Sequence↗
PubMed1994

Effects of cholecystokinin (CCK) and other secretagogues on isoforms of protein kinase C (PKC) in pancreatic acini.

We used rat pancreatic acini and measured the effects of various agents on digestive enzyme secretion, diacylglycerol (DAG) and the cellular distribution of protein kinase C (PKC) enzyme activity as well as isoforms of PKC determined by quantitative immunoblot analysis. TPA, but not CCK-8, caused translocation of PKC enzyme activity from the cytosol fraction to the membrane fraction. Immunoblot analysis detected PKC-alpha, PKC-delta, PKC-epsilon and PKC-zeta. PKC-beta, PKC-gamma and PKC-eta were not detected. TPA caused translocation of all isoforms from cytosol to membrane, whereas CCK-8 caused translocation of PKC-delta and PKC-epsilon, carbachol caused translocation of PKC-epsilon, and bombesin and secretin caused no detectable translocation of any isoform. Specific receptor antagonists could prevent, as well as reverse completely, the translocation of PKC isoforms caused by CCK-8 or carbachol. Agonists added in sequence with an interposed addition of a specific receptor antagonist caused cycling of PKC-epsilon between cytosol and membrane fractions. Each receptor-mediated agonist that caused translocation of PKC also increased DAG, and with CCK-8 and carbachol cycling of PKC-epsilon between cytosol and membrane was accompanied by corresponding cyclic changes in cellular DAG. CCK-JMV-180, bombesin and secretin increased DAG but did not cause translocation of any PKC isoform. Translocation of a PKC isoform could be accounted for by whether the increased DAG originated from PIP2 (accompanied by translocation) or from phosphatidylcholine (no accompanying translocation). Thus it appeared that DAG, in pancreatic acini, is functionally compartmentalized depending on the source of the lipid. Studies using CCK-8 and CCK-JMV-180 indicated that occupation of the low affinity state of the CCK receptor by either peptide increased DAG from phosphatidylcholine, whereas occupation of the very low affinity state by CCK-8 increased DAG from PIP2 and caused translocation of PKC-delta and PKC-epsilon. TPA stimulated amylase secretion, indicating that activation of PKC can stimulate enzyme secretion; however, with the various receptor-mediated secretagogues there was no consistent, unequivocal correlation between translocation of an isoform of PKC and accompanying changes in enzyme secretion.

Amylases↗
PubMed1993

Human tau isoforms confer distinct morphological and functional properties to stably transfected fibroblasts.

Tau protein is a neuronal microtubule-associated protein that promotes the assembly and stability of microtubules. To evaluate the biological significance of tau isoform diversity, NIH-3T3 cells were stably transfected with cDNAs encoding each of the six isoforms present in human brain. Cells expressing different isoforms developed distinct morphologies. Cell lines expressing 3-repeat tau isoforms developed large flat cell bodies while cells expressing 4-repeat isoforms had small, round cell bodies. All transfected cell lines, except those expressing the shortest tau isoform, displayed very long thin neurite-like processes. Tau colocalized with microtubules in both the cell body and the long processes in all of the tau-transfected cells. Tau also displayed a diffuse amorphous staining pattern that was concentrated around the cell nucleus. Microtubule bundling was not enhanced in any of the transfected cells as compared to untransfected controls. The transfected cells showed increased resistance to colchicine treatment. Thus, different tau isoforms can confer unique cellular morphologies to 3T3 cells and can alter the susceptibility of these cells to a microtubule depolymerizing agent.

3T3 Cells↗
PubMed1991

Either isoform of the dopamine D2 receptor can mediate dopaminergic repression of the rat prolactin promoter.

Hypophyseal portal dopamine is a major negative regulator of pituitary prolactin (PRL) production. Dopamine has been reported to repress PRL gene transcription in pituitary cells. To facilitate further study of the effect of dopamine on PRL gene activation, we introduced PRL promoter and D2 receptor (D2R) constructs into GH3 cells. Since two D2R isoforms (termed D2S and D2L) have been cloned previously, we first determined which isoform(s) is present in the lactotroph by measuring the level of each mRNA species in rat prolactinoma. mRNA for each D2R isoform was found to be present, with the D2L mRNA in great (c. 6-fold) excess. Because the lactotroph contains both isoforms, the effect of each on the PRL promoter was investigated. The cDNA for each receptor isoform was synthesized by polymerase chain reaction, and cloned into an RSV-based expression vector. GH3 cells were then transiently co-transfected with either of the resulting RSV-D2R constructs plus a PRL-chloramphenicol acetyltransferase (CAT) construct containing the first 1957 base-pairs of PRL gene 5'-flanking DNA. The cells were then incubated 48 h plus or minus the dopamine agonist ergocryptine (ECR). In the presence of either RSV-D2R isoform, ECR yielded a 4-5-fold decrease in CAT activity, an effect not seen in the absence of the RSV-D2R. The promoter specificity of this effect was demonstrated by the inability of ECR to regulate expression of a control RSV-CAT construct. The PRL promoter repression mediated by each receptor isoform had appropriate pharmacology: the specific D2R agonist, quinpirole, yielded results similar to ECR, and the ECR repression was reversed by the dopamine antagonist spiperone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Functional ovarian and placental isoforms of porcine aromatase.

Functional isoforms of porcine aromatase cytochrome P-450 were cloned from placenta, and ovarian theca interna and granulosa tissues, and full length cDNAs were expressed in vitro. Porcine theca and granulosa expressed an identical form of P-450arom. This ovarian cDNA encoded for a protein of 501 amino acids, two amino acids shorter at the N-terminal end than placental P-450arom isoform (503 residues). Overall, the two isoforms exhibited 93% nucleotide and 87% amino acid identity with each other, and both were highly homologous, at the nucleotide and amino acid levels, to human and bovine P-450arom, also 503 amino acid proteins. Analysis of the predicted amino acid sequence further suggested that the regions of the cDNAs, corresponding to presumed exons III, V and IX, assuming conservation of intron-exon boundaries with the human P-450arom gene, were conserved in the porcine placental and ovarian enzymes, while sequence variance occurred in all other putative exons. In vitro expression indicated that the cDNA encoding porcine placental P-450arom was almost 10-fold more active in the synthesis of estrone from androstenedione than was the ovarian isoform which synthesized more 19OH-androstenedione than estrone. Western analysis of transfected Cos1 cells suggested that the differences in activity were not due to levels of expression of the cDNAs since similar levels of immunodetectable protein were observed in cells transfected with each construct. Both isoforms were sensitive to inhibition of activity by the specific aromatase inhibitors, 4OH-androstenedione and CGS16949A. In addition, activity of the enzyme encoded by the ovarian P-450arom cDNA was suppressed by etomidate, an inhibitor of cytochrome P-450 11beta-hydroxylase, but the placental P-450arom isoform was not. These functional differences were consistent with observations made in similar experiments involving P-450arom activity in freshly homogenized tissues. These data provide evidence of the existence of distinct, intraspecies isoforms of P-450arom, the first described in any species and suggest that pigs possess a unique mechanism for regulating androgen metabolism.

Amino Acid Sequence↗
PubMed1994

Expression of protein kinase C isoforms in skin papilloma and carcinoma of mice.

Expression of protein kinase C isoforms at the mRNA level was examined with papilloma and carcinoma of mouse skin. Of the nine isoforms examined, the alpha, delta and eta isoforms were expressed in papilloma and carcinoma at high levels, whereas expressions of beta, epsilon and zeta isoforms were very weak. No or little signals for the gamma and theta isoforms were observed in skin tumors. When compared with normal skin, only the delta isoform was highly expressed in carcinoma at about 2-fold the normal skin or papilloma, while the remaining isoforms were at a similar level to normal skin.

Animals↗
PubMed1995

Characterization of muscle glyceraldehyde-3-phosphate dehydrogenase isoforms from euthermic and induced hibernating Jaculus orientalis.

The specific activity of D-glyceraldehyde-3-phosphate (G3P) dehydrogenase (phosphorylating) (GPDH, EC 1.2.1.12) found in skeletal muscle of induced hibernating jerboa (Jaculus orientalis) was 3-4-fold lower than in the euthermic animal. The comparative analysis of the soluble protein fraction of these tissues by SDS-PAGE and Western blotting showed a significant decrease in the intensity of a protein band of about 36 kDa, the GPDH subunit, in hibernating jerboa. After using the same purification procedure, the GPDH from muscle of hibernating jerboa exhibited lower values for both apparent optimal temperature and specific activity than the enzyme from the euthermic animal. Non-linear Arrhenius plots were obtained in both cases, but the Ea values calculated for the GPDH from hibernating tissue were higher. Although in both purified enzyme preparations three isoelectric GPDH isoforms, exhibiting pI values in the range 8.2-7.5, were resolved by chromatofocusing, clear differences were observed in these preparations concerning the relative contribution to the total enzymatic activity of the two main isoforms, named GPDH I (pI values, 8.1-8.2) and GPDH II (pI values, 7.8-7.9). Thus, whereas GPDH I was the major isoform purified from euthermic muscle, accounting for more than 90% of the total activity, the amount of activity due to GPDH II reached up to 65% in preparations of hibernating jerboa. All isoforms exhibited similar native and subunit molecular masses and cross-reacted with an anti-GPDH antibody raised against the GPDH I. However, the two muscle GPDH isoforms prevailing under hibernating conditions exhibited a decreased catalytic efficiency when compared with the corresponding major isoforms purified from euthermic animals, as indicated by their different specific activities and kinetic parameters, i.e. relatively high Km and low Vmax values. Since the glycolytic flow has been found to be widely reduced in skeletal muscle of induced hibernating jerboa, the changes in the GPDH isoforms described in the present study could provide a molecular basis to explain some of the metabolic changes associated with mammalian hibernation.

Animals↗
PubMed1991

Isoforms of turkey prolactin: evidence for differences in glycosylation and in tryptic peptide mapping.

1. Three isoforms of turkey pituitary prolactin have been isolated, including a nonglycosylated isoform of 22,500 mol. wt and two glycosylated isoforms of 24,500 mol. wt. 2. The glycosylated turkey prolactins differed in carbohydrate composition, with one isoform apparently containing only O-linked carbohydrate. 3. Tryptic peptide maps showed a few peptides distinctly different among the three prolactin isoforms. 4. Amino acid sequencing of the first 40 residues of the three prolactin isoforms showed arginine at position 24 and histidine at position 27, for the nonglycosylated form, but no identifiable amino acids were detected at this position for the glycosylated isoforms.

Amino Acid Sequence↗
PubMed1995

Comparison of different techniques for the analysis of metallothionein isoforms by capillary electrophoresis.

We have investigated free-solution capillary electrophoresis (FSCE) and micellar electrokinetic capillary chromatography (MECC) separations of metallothionein (MT) isoforms conducted in uncoated and surface-modified fused-silica capillaries. At alkaline pH, FSCE rapidly resolves isoforms belonging to the MT-1 and MT-2 charge classes. At acidic pH, additional resolution of MT isoforms is achieved. The use of high-ionic-strength (0.5 M) phosphate buffers can result in high peak efficiencies and increased resolution for some MT isoforms. Interior capillary surface coatings such as polyamine and linear polyacrylamide polymers permit separation of MT isoforms with enhanced resolution through their effects on electroosmotic flow (EOF) and protein-wall interactions. Improvements in MT isoform resolution can also be achieved by MECC using 100 mM borate buffer pH 8.4 containing 75 mM SDS. Deproteinization of tissue cytosol samples with acetonitrile (60-80%) or perchloric acid (7%) produces extracts that can be subjected to direct analysis of MT by FSCE or MECC. We conclude that optimal separation of MT isoforms by capillary electrophoresis (CE) can be achieved with the appropriate combination of different capillaries, buffers and sample preparation techniques.

Animals↗
PubMed2006

Enzymatic and biochemical properties of a novel human serine dehydratase isoform.

A cDNA clone similar to human serine dehydratase (SDH) is deposited in the GenBank/EMBL databases, but its structural and functional bases remain unknown. Despite the occurrence of mRNA, the expected protein level was found to be low in cultured cells. To learn about physicochemical properties of the protein, we expressed the cDNA in Escherichia coli, and compared the expressed protein with that of a hepatic SDH. The purified protein showed l-serine and l-threonine dehydratase activity, demonstrating to be an isoform of SDH. However, their Km and Vmax constants were different in a range of two-order. Removal of Pro128 from the hepatic SDH consisting of 328 residues, which is missing in the corresponding position of the isoform consisting of 329 residues, significantly changed the Michaelis constants and Kd value for pyridoxal 5'-phosphate, whereas addition of a proline residue to the isoform was without effect. These findings suggest the difference in the structures of the active sites of the two enzymes. Another striking feature was that the expressed level of the isoform in E. coli was 7-fold lower than that of the hepatic SDH. Substitution of Val for Leu287 in the isoform dramatically increased the protein level. The high yield of the mutated isoform was also confirmed by the in vitro transcription and translation experiment. The poor expression of the isoform could be explained by the more stable secondary structure of the mRNA than that of the hepatic SDH mRNA. The present findings may provide a clue as to why the protein level in cultured cells is low.

Amino Acid Sequence↗
PubMed2006

Genomic organisation of the mouse gene encoding endothelin-converting enzyme-1 (ECE-1) and mRNA expression of ECE-1 isoforms in murine tissues.

Mouse knockout-models have previously revealed important biological functions of endothelin-converting enzyme-1 (ECE-1) in normal cardiac and craniofacial development. Since human ECE-1 is expressed in various isoforms, termed a, b, c, and d, expression of which is controlled by alternative promoters, we postulated that corresponding isoforms may also be transcribed from the murine Ece1 gene. By comparative sequence analysis using exon-specific sequences of human and rat ECE-1 we have resolved the complete exon-intron structure of the murine Ece1 locus on chromosome 4. The murine Ece1 gene comprises 23 exons distributed over 100 kb of genomic DNA and was found to be structurally highly conserved when compared to the human ECE1 gene. As with the human gene, the exons containing isoform-specific sequences were localised in the 5' terminal region of the murine Ece1 gene. Using specific sense primers, isoform-specific expression of murine ECE-1 mRNA in various mouse tissues was confirmed by RT-PCR. Using real-time PCR we demonstrated that ECE-1c was the most abundantly expressed isoform in most tissues, except for heart and aorta displaying a more even isoform distribution. We detected an additional isoform-specific exon, designated c2, which was apparently constitutively spliced and expressed only as minor fraction of ECE-1c transcripts. Our results provide evidence of structural conservation of mammalian genes encoding ECE-1 and will facilitate a more refined analysis of ECE-1 mRNA expression in the mouse model organism.

Algorithms↗
PubMed2005

Early and delayed glutamate effects in rat primary cortical neurons. Changes in the subcellular distribution of protein kinase C isoforms and in intracellular calcium concentration.

Glutamate-induced changes in the subcellular distribution of protein kinase C isoforms and in the intracellular calcium concentration were investigated in rat primary cortical neurons. Western blot analysis of protein kinase C isoforms (alpha, beta1, beta2, gamma, delta, epsilon, zeta and theta), performed 30 min after a 10 min treatment with 30 microM glutamate, revealed a decrease in the total beta1 (-24%) and beta2 (-40%) isoform levels, without any significant change in any of the other isozymes. All conventional isoforms translocated to the membrane compartment, while delta, epsilon, zeta and theta; maintained their initial subcellular distribution. Twenty-four hours after glutamate treatment, the total protein kinase C labelling had increased, particularly the epsilon isoform, which accounted for 34% of the total densitometric signal. At this time, protein kinase C beta1, delta, epsilon and zeta isoforms were mainly detected in the membrane compartment, while gamma and theta; signals were displayed almost solely in the cytosol. Basal intracellular calcium concentration (FURA 2 assay) was concentration-dependently increased (maximum effect +77%) 30 min, but not 24h after a 10 min glutamate (10-100 microM) treatment, while the net increase induced by electrical stimulation (10 Hz, 10s) was consistently reduced (maximum effect -64%). The N-methyl-d-aspartate receptor antagonist, MK-801, 1 microM, prevented glutamate action both 30 min and 24 h after treatment, while non-selective protein kinase C inhibitors, ineffective at 30 min, potentiated it at 24 h. These findings show that protein kinase C isoforms are differently activated and involved in the early and delayed glutamate actions, and that the prevailing effect of their activation is neuroprotective.

Algorithms↗
PubMed2005

Role of molecular isoforms of acetylcholinesterase in learning and memory functions.

In the present study, activity of salt soluble (SS) G1 and detergent soluble (DS) G4 molecular isoforms of acetylcholinesterase (AChE) has been investigated in rat brain areas in trained (learned), scopolamine (amnesic) and Tacrine (anti-dementic) treated rats to find out their role in learning and memory functions. AChE was estimated spectrophotometrically at 412 nm in rat brain areas. Isolation and partial purification of molecular isoforms G1 and G4 of AChE was done by gel filtration chromatography. Passive avoidance was used to test learning and memory functions. AChE activity was altered in both the fractions SS and DS of different brain areas following passive avoidance in control, scopolamine treated, tacrine treated and tacrine treatment in scopolamine pretreated rats. The peak AChE activity obtained in the DS (fraction 9) and the SS (fraction 13) fraction following gel filtration chromatography. On the basis of molecular weight fraction 9 (DS) and 13 (SS) represent the G4 and G1, respectively. The pattern of changes in the AChE activity of G1 isoform (fraction 13 of SS) and G4 isoform (fraction 9 of DS) in brain areas were similar to those of SS and DS fraction, respectively. In hippocampus, AChE activity in the fraction G1 isoform (fraction 13 of SS) was decreased only in tacrine treated rats but AChE activity in the G4 isoform (fraction 9 of DS) was decreased in both trained and tacrine treated rats. Changes in activity of G4 isoform of AChE in hippocampus could be correlated with passive avoidance learning, scopolamine induced deficit in passive avoidance and reversal of scopolamine deficit by tacrine.

Acetylcholinesterase↗