Cholinesterases (acetylcholinesterase and butyrylcholinesterase) exhibit additional catalytic activities apart from their well-known action in hydrolyzing choline esters. An amine-sensitive aryl acylamidase activity is exhibited by both acetyl- and butyrylcholinesterases. A metallocarboxypeptidase-like activity is found associated with both acetyl- and butyrylcholinesterases. The peptidase activity exhibited by butyrylcholinesterase was located in a 50-kDa COOH-terminal fragment. Acetylcholinesterase is implicated in noncholinergic functions in the substantia nigra. A relationship between tumorigenesis, cell differentiation, and cholinesterases has been speculated. The sequence similarities between different esterases, lipases, thyroglobulin, cell adhesion proteins, and cholinesterases would make it appear that cholinesterases are capable of exhibiting more than one biological activity and their functions are wider than what is hitherto known.
Abstract— Lipid peroxide formation as measured by the thiobarbituric acid reaction was demonstrated in subcellular fractions of rat brain. The ascorbic acid induced nonenzymic lipid peroxidation was distributed in all the subcellular fractions with a maximum in microsomes. The NADPH dependent enzymic lipid peroxidation occurred mainly in microsomes and to a smaller extent in synaptosomes; NADH could replace NADPH for the enzymic lipid peroxidation under the assay conditions employed. Fe2+ but not Fe3+ stimulated the NADPH or NADH dependent lipid peroxide formation. The optimum conditions with respect to pH, ascorbic acid or NADPH concentration, time of incubation and protein concentration were studied. Heating the microsomes at 100oCdid not influence the ascorbate‐induced lipid peroxidation but completely abolished the NADPH linked peroxidation. Several heavy metal ions, surface active agents and EDTA were inhibitory to lipid peroxidation. The effect of thiol agents indicated that ‐SH groups were involved in the enzymic lipid peroxidation. Studies on subcellular fractions of developing rat brain showed an increasing trend in lipid peroxidation with the advancing age of the animal. No significant difference in lipid peroxidation was observed between brains from normal rats and those from rats affected by experimental allergic encephalomyelitis.
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.
The pulsed electrodeposition of copper on stainless steel has been studied in copper sulphate bath and the effect of duty cycle and frequency on the thickness and current efficiencies were compared at 50°C and at room temperature with average current density of 4 A dm−2. A new strike bath based on cupric chloride and hydrochloric acid was developed for the first time. The Cu coatings were characterised by SEM, AFM and XRD. Crystallite sizes of Cu coatings were calculated for various duty cycles from the Scherer's equation. The deposits were smaller nodules and fine grained.
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