Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.8 (cholinesterase)
 12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiotoxin, protamine and polylysine are potent inhibitors of various cholinesterases. CaCl2 and MgCl2 overcome the inhibition. The order of addition of the inhibitor and the protecting agent (MgCl2) influences the final degree of the inhibition observed. These findings suggest that cardiotoxin, protamine and polylysine inhibit cholinesterases by the ionic binding of their basic groups with the anionic sites of cholinesterase molecules.
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PMID:Mechanism of anticholinesterase activities of cardiotoxin, protamine and polylysine. 84 58

The effect of hypoparathyroidism and low blood calcium on enzyme levels in rat liver and kidney is shown. Four animal groups were used: parathyroidectomized (PTX), PTX with CaCl2 added in the drinking water, sham-operated controls and sham-operated with CaCl2 added in the drinking water. PTX significantly lowered serum parathyroid hormone (PTH) and calcium. Supplementation of CaCl2 in the drinking water increased serum Ca levels in PTX rats but not in the controls. Significant changes in several liver and kidney enzymes were seen. Most affected were the liver NADP dependent enzymes, glucose-6-phosphate dehydrogenase and malic enzyme. Similar patterns but with relatively smaller changes were seen in the liver enzymes, lactic dehydrogenase, hexokinase, and aspartate transferase. No significant differences between the groups were seen in the levels of malic dehydrogenase, isocitric dehydrogenase, fructose-6-phosphate kinase and cholinesterase. In the kidney, which was less affected than the liver, the only significant difference was seen in the level of malic enzyme. Serum total lipids in the PTX group were significantly lower. All the changes seen were partially reversed by Ca supplementation in the drinking water.
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PMID:Biochemical change in the liver and kidney of rats following parathyroidectomy. 400 1

1. Changes in end-plate channel properties resulting from substitution of Sr2+ for Ca2+ in the Ringer solution have been analysed at the voltage clamped frog end-plate, by recording m.e.p.c.s and ACh induced noise variance. 2. In 2 mM-Sr2+--Ringer the peak size of m.e.p.c.s showed a very small increase, and the time constant of the decay phase (tau m.e.p.c.), at any given voltage, was increased by a factor of about two compared to control Ringer. The voltage dependence of tau m.e.p.c. was the same in both solutions. 3. Addition of increasing amounts of CaCl2 to 2 mM-Sr2+--Ringer produced a progressive shortening of tau m.e.p.c., with no change in voltage dependence. 4. Estimates of single channel properties from noise analysis showed that the elementary conductance appeared to be slightly increased in 2 mM-Sr2+--Ringer, whilst the mean channel life-time was prolonged by a factor of about two. These changes in single channel properties are sufficient to account for the observed changes in m.e.p.c.s. 5. Following inhibition of cholinesterase activity by neostigmine, similar effects on m.e.p.c.s and single channel properties were still observed on changing to 2 mM-Sr2+--Ringer. The shapes of m.e.p.c.s in Sr2+ + neostigmine Ringer were often altered, and showed flat 'plateaus'. 6. The observed effects of Sr2+--Ringer on channel life-time cannot be explained on the basis of changes in surface charge density on the membrane, and suggest that divalent cations have an additional, and more direct, influence on receptor channel properties.
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PMID:Effects of strontium ions on end-plate channel properties. 625 99

Although aspirin (acetylsalicylic acid) is negatively charged, it is hydrolysed by butyrylcholinesterase (BuChE). Catalytic parameters were determined in 100 mM Tris buffer, pH 7.4, in the presence and absence of metal cations. The presence of Ca2+ or Mg2+ (<100 mM) in buffer did not change the Km, but accelerated the rate of hydrolysis of aspirin by wild-type or D70G mutant BuChE by 5-fold. Turnover numbers were of the order of 5000-12000 min-1 for the wild-type enzyme and the D70G and D70K enzymes in 100 mM Tris, pH 7.4, containing 50 mM CaCl2 at 25 degreesC; Km values were 6 mM for wild-type, 16 mM for D70G and 38 mM for D70K. People with 'atypical' BuChE have the D70G mutation. The apparent inhibition seen at high aspirin concentration was not due to inhibition by excess substrate but to spontaneous hydrolysis of aspirin, causing inhibition by salicylate. The wild-type and D70G enzymes were competitively inhibited by salicylic acid; the D70K enzyme showed a complex parabolic inhibition, suggesting multiple binding. The effect of salicylate was substrate-dependent, the D70K mutant being activated by salicylate with butyrylthiocholine as substrate. Km value for wild-type enzyme was lower than for D70 mutants, suggesting that residue 70 located at the rim of the active site gorge was not the major site for the initial encounter aspirin-BuChE complex. On the other hand, the virtual absence of affinity of the W82A mutant for aspirin indicated that W82 was the major residue involved in formation of the Michaelis complex. Molecular modelling of aspirin binding to BuChE indicated perpendicular interactions between the aromatic rings of W82 and aspirin. Kinetic study of BuChE-catalysed hydrolysis of different acetyl esters showed that the rate limiting step was acetylation. The bimolecular rate constants for hydrolysis of aspirin by wild-type, D70G and D70K enzymes were found to be close to 1x106 M-1 min-1. These results support the contention that the electrostatic steering due to the negative electrostatic field of the enzyme plays a role in substrate binding, but plays no role in the catalytic steps, i.e. in the enzyme acetylation.
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PMID:Butyrylcholinesterase-catalysed hydrolysis of aspirin, a negatively charged ester, and aspirin-related neutral esters. 974 94