Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.7 (acetylcholinesterase)
 28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Red blood cell plasma membranes contain a number of enzymes: ATPases, anion transport protein, glyceraldehyde 3-phosphate dehydrogenase, protein kinases, adenylate cyclase, acetylcholinesterase. Most of them are tightly bound to the membrane and are present in small amounts. As a result, structural characterization of erythrocyte membrane enzymes has not yet been successful. Functional studies have, however, yielded a great deal of information. ATPases allow active transport of cations (calcium, sodium, potassium). Anion transport protein controls movements of chloride and phosphate ions, and of glucose and water. Among glycolytic enzymes: glyceraldehyde 3-phosphate dehydrogenase is partially bound to the membrane. Protein kinases catalyze the phosphorylation of several membrane proteins, one of which (spectrin) is involved in red blood cell mechanical properties. The physiological role of adenylate cyclase is unknown. Acetylcholinesterase is an ectoenzyme. Calcium-dependent ATPase, adenylate cyclase and phosphorylation of erythrocyte membrane proteins have been found abnormal in various conditions: hereditary spherocytosis, sickle-cell anemia, progressive muscular dystrophies, all of these disorders being associated with a decreased deformability of the erythrocyte.
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PMID:The enzymes of the red blood cell plasma membrane. 14 25

Erythrocytes from a heterogeneous group of hemolytic anemias have been found to release acetylcholinesterase-enriched fragments and show myelin forms during ATP depletion in vitro. The highest amount of fragmentation was found in hereditary spherocytosis and xerocytosis, two inherited membrane defects. Our data suggest ATP depletion plays a role in producing fragmentation or myelin forms. The addition of external CaCl2 1 mM had no effect on the degree of fragmentation. However, propranolol hydrochloride, a cationic anesthetic that does not prevent ATP depletion, inhibited fragmentation and the appearance of myelin forms in both hereditary spherocytes and xerocytes. A more detailed study of the xerocyte fragments showed that they had the same protein composition as those from normal red cells, primarily integral membrane proteins and glycoproteins. The red cells from patients with PNH and G6PD deficiency had the shortest survival in vivo (51Cr) and produced the smallest amount of fragmentation and myelin forms in vitro, whereas xerocytosis with only mild to moderate hemolysis in vivo was associated with the highest amount of myelin forms and membrane fragments in vitro.
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PMID:Fragmentation and myelin formation in hereditary xerocytosis and other hemolytic anemias. 68 29

Erythrocytes from individuals with Hereditary Spherocytosis (HS) were fractionated on Percoll density gradients. The osmotic fragility, mean cell volume, mean cell haemoglobin concentration, reticulocyte count and cell morphology of the fractions showed that the gradients separate the erythrocytes according to age, the older small spherocytes appearing in the dense fractions. Comparison of the well established parameters of erythrocyte ageing, pyruvate kinase activity, acetylcholinesterase activity and cell potassium content in normal and HS erythrocyte fractions of similar age revealed abnormalities in the senescence of HS erythrocytes both before and after splenectomy.
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PMID:Abnormal pattern of erythrocyte ageing in hereditary spherocytosis as shown by Percoll density gradient centrifugation. 647 27

Acetylcholinesterase of human erythrocytes from healthy donors and from patients with hematological disorders was analysed in a search for differential membrane parameters. Two substrates were used to estimate the exposure of acetylcholinesterase active site in the membrane: phenylacetate, a hydrophobic substrate, to determine total enzyme activity, and acetylcholine, an ionic substrate, to measure the externally reactive enzyme. The sensitivity of acetylcholinesterase to added stearic acid was also analysed. Three categories of the disorders studied were discerned: (a) The erythrocyte acetylcholinesterase profile was indistinguishable from normal control in beta-thalassemia minor and groups of patients with autoimmune hemolytic anemia or congenital dyserythropoietic anemia type II. (b) A marked decline in acetylcholinesterase with both substrates and reduced sensitivity to stearic acid were exhibited by the erythrocytes of paroxysmal nocturnal hemoglobinuria, beta-thalassemia major and other autoimmune hemolytic anemia and congenital dyserythropoietic anemia type II patients. Normal erythrocytes, either aged or pretreated to 50 degrees C, also showed similar characteristics. (c) Hereditary spherocytosis was singly differentiated by an elevated acetylcholinesterase activity with acetylthiocholine and by a vastly diminished sensitivity to stearic acid, while activity with phenylacetate was equal to control. This distinct profile may reflect the unique organization of the erythrocyte membrane in hereditary spherocytosis.
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PMID:Unique profile for erythrocyte membrane acetylcholinesterase in hereditary spherocytosis. 684 70

Broadly speaking, the red cell membrane is comprised of --a cholesterol-rich phospholipid bilayer that is studded by a large number of trans-bilayer proteins, --of glycosylphosphatidylinositol-anchored proteins (GPI-proteins) standing outside, and --an important protein assembly, the erythrocyte or membrane skeleton, that laminates the inner surface of the bilayer. Among the trans-bilayer proteins, one finds the anion exchanger, the glycophorins, the glucose transporter, a variety of cation transporters and pumps, and of course proteins carrying the epitopes of many blood groups. Among the GPI-proteins, one encounters the acetylcholinesterase and the decay-accelerating factor (CD 55). Among the skeletal proteins, finally, one recognises spectrin, actin (and a number of actin-binding proteins other than spectrin: dematin, tropomyosin, tropomodulin, etc.), protein 4.1 and protein p55. Spectrin heterotetramer organizes into a bidimensional network with a hexagonal mesh on the average. This network is linked to trans-bilayer proteins, through the complex beta-spectrin-ankyrin-anion exchanger (+ protein 4.2) on the one hand and, on the other hand, through the triangular interaction between protein 4.1, glycophorin C and protein p55. The sequence of the above proteins and the exon-intron organisation of their genes are known in most cases. Many proteins have a widespread tissue distribution in the form of variants adapted to their local functions. Such variants may be the products of multigene families (anion exchanger, ankyrin, spectrin), or derive from a single gene (protein 4.1, protein 4.2), the transcripts of which undergo cell-specific alternative splicing. It has been established that many congenital haemolytic anaemias result from mutations altering the above-mentioned genes. We will provide two examples. Hereditary elliptocytosis stems from an array of mutations located at, or near the head-to-head self-association region of two spectrin alpha beta dimers, or from mutations which, most often, yield a reduction (heterozygous state) or the lack (homozygous state) of protein 4.1. The aggravation of elliptocytosis associated with alpha-spectrin mutations frequently yields poikilocytosis and usually stems from the occurrence, in trans, of a low expression allele, allele alpha LELY. Hereditary spherocytosis derives from mutations in the ankyrin gene (80% of the cases), the anion exchanger gene (10-15% of the cases), the protein 4.2 gene (rare cases) and the alpha- and beta-spectrin genes (rare cases). Anion exchanger mutations usually cause the decrease in this protein (heterozygous state).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Red cell membrane polypeptides under normal conditions and in genetic disorders. 854 17