Effect of essential fatty acid deficiency on the arrhenius plot of acetylcholinesterase from rat erythrocytes (original) (raw)
1974, The Journal of nutrition
The allosteric character of the acetyl cholinesterase from rat erythrocytes has been described in a previous paper (1). It was also reported there that the enzyme loses its allosteric ‘behavior when bound to EFA-deficient membranes. Similar be havior has been reported for other en zymes ‘boundto erythrocyte (2â€"4) and microsomal (5) membranes. It was later demonstrated that the allosteric behavior of the membrane-bound acetyicholinester ase and (Na@ + K@)-ATPase correlated with the overall fluidity of the membrane fatty acids, where the EFA did not play a particular role (6). However, it was pointed out that a direct correlation exists between the cooperativity of the mem brane-bound acetyleholinesterase and the linoleic fatty acid content of the erythro cyte lipids. This correlation was not found between the enzyme cooperativity and the total EFA content of the membrane (6). We have described (4) that the Arrhenius plot of the (Mg2@+ K@) p-nitrophenyl phosphatase from EFA-deficient and EFA sufficient rats is clearly different. It was of interest to test whether these temperature dependent changes were specific for EFA deficiency or, as the allosterism, correlated with the overall membrane fluidity.
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Biochimica et Biophysica Acta (BBA) - Biomembranes, 1973
Studies were carried out to determine the Hill coefficients for the inhibition by F-of the erythrocyte membrane-bound Mg/+-ATPase, (Na + +K+)-ATPase and acetylcholinesterase from rats fed with seven different diets. Five groups were fed with different natural fats or oil supplements, one with a hydrogenated fat supplement and the other with fat-free diet. The responses of the red cell fatty acids to dietary fats were recorded. The values of n for the inhibition by F-of the three enzymes revealed a particular and different behaviour in each group. Correlations between the fatty acid compositions of erythrocyte membranes and cooperativity of each enzyme were calculated. The results indicate that neither the essential fatty acid family nor the non-essential ones are particularly involved in the allosteric phenomena. The increase of the double bond index/saturation ratio of fatty acids, which is taken as indicative of membrane fluidity, was accompanied in an inverse manner by changes in allosteric transitions of the (Na + +K+)-ATPase and acetylcholinesterase, whereas the Mg 2+-ATPase was not dependent on this ratio. Diminution of membrane fluidity, carried out by in vitro increase of its cholesterol content, yields confirmatory results of this regulatory mechanism since the value ofn for acetylcholinesterase shifted as predicted. These facts indicate that the membrane fluidity is a physiological regulator for the allosteric behaviour of the membrane-bound enzymes and that each enzyme exhibits a particular behaviour in this phenomenon.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1972
The allosteric behavior of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) from red cell ghosts of rats fed fat-sufficient and fat-deficient diets was investigated. Allosteric type kinetics with n =-1.6 have been obtained for the inhibition by Fin rats fed a fat-sufficient diet. In animals fed a fat-deficient diet the values of n changed from-1.6 to-I.O. When these animals were then fed a fat-sufficient diet the values of n shifted from-I.O to-1.6. This in vivo reversion was obtained after 8 days of refeeding. Two types of changes in the values of n were obtained in vitro in fat-deficient rats: (I) from-I.O to-I.6 by solubilization of the membrane-bound enzyme with Triton X-Ioo, (2) from-1.6 to-I.O by resconstitution of the membrane-like structure from the soluble enzymatic preparation. The possibility that the structure of the membrane could be responsible for the changes in the phenomenon of phenotypic allosteric desensitization in the membrane-bound enzymes is discussed
The Biochemical journal, 1988
The temperature-dependence of both the lipid order parameter (SDPH) and acetylcholinesterase (AChE) activity from native and cholesterol-enriched human erythrocyte membranes was investigated. Cholesterol enrichment abolishes an inflection observed around 30 degrees C in the temperature-dependence of native membrane lipid order parameter, whereas the Arrhenius plot of the enzymic activity is substantially unaffected. These results support the view that the breaks in the Arrhenius plot of the enzyme activity are not related to sudden changes of bulk membrane physical state, but arise from a direct effect of temperature on enzyme conformation.
IUBMB Life, 1997
The activity characteristics of membrane acetylcholinesterase from red blood cells of diabetic patients are very different from those of healthy donors: the limiting enzyme reaction rate is 17.2 + 0.8 ~tmol acetylthiocholine per ml packed cells per min compared with 13.1 + 0.8 grnol for control cells. The Michaelis constants for subs,rate are the same: 0.061 + 0.007 mM for diabetic and 0.061 + 0.004 mM for control cells 9 Cell exposure to oxidative agent (t-butyl hydroperoxide) significantly changes the enzyme activity parameters. The limiting enzyme reaction rate increases but the affinity for the subs,rate decreases at lower oxidant concentrations (up to 0.1 mM for the "diabetic" erythrocytes and up to 0.4 mM for the control ones). At higher oxidant concentrations both the limiting reaction rate and the Michaelis constant decrease. The susceptibility of erythrocyte membranes of diabetic patients to oxidative stress is much higher in comparison with control erythrocyte membranes.
Journal of Molecular and Cellular Cardiology, 1987
19, 465-475. Three groups of male, weanling, Sprague--Dawley rats were fed diets containing 7% hydrogenated coconut oil, 6.6% hydrogenated coconut oil + 0.4% corn oil, or 7% corn oil for 8-17 weeks. These diets provided 0% (EFAD group), 0.5% (MEFAD group) or 5% (CONTROL group) of the total energy as linoleic acid, respectively. Crude plasma membranes were prepared from heart and assayed for adenylate cyclase activity. Both basal and fluoride-stimulated activity was lower in the membranes from EFAD and MEFAD rats than that of the controls. The double bond index of total lipids and phospholipids, and fluorescence polarization of 1,6-diphenyl-l,3,5-hexatriene (DPH) were not appreciably different in the membranes from the three dietary groups. The fatty acid composition of total phospholipids of the membranes, however, was quite different and indicative of biochemical changes typical of an EFA deficiency. Feeding of the control diet to the EFAD or MEFAD rats for up to 6 weeks did not alleviate completely the changes in adenylate cyclase activity although the fatty acid patterns were restored to the normal levels. There was also a decrease in the number of [3H]-DHA binding sites in heart of EFAD rats as compared with their controls. The results suggest that the changes induced by EFA deficiency in the acyl group composition of membrane phospholipids and in the number of beta-adrenergic receptors may be important in regulating adenylate cyclase activity in the heart. activity, [SH]-Dihydroalprenolol binding and fatty acid composition of rat heart membranes in essential fatty acid deficiency [Abstract] Fed Proc 45, 1026 (1986) #5069.
Human Erythrocyte Acetylcholinesterase in Health and Disease
Molecules, 2017
The biochemical properties of erythrocyte or human red blood cell (RBC) membrane acetylcholinesterase (AChE) and its applications on laboratory class and on research are reviewed. Evidence of the biochemical and the pathophysiological properties like the association between the RBC AChE enzyme activity and the clinical and biophysical parameters implicated in several diseases are overviewed, and the achievement of RBC AChE as a biomarker and as a prognostic factor are presented. Beyond its function as an enzyme, a special focus is highlighted in this review for a new function of the RBC AChE, namely a component of the signal transduction pathway of nitric oxide.
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