Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.1.1.8 (
cholinesterase
)
12,691
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The effect of chemical modification on the
pseudocholinesterase
and aryl acylamidase activities of purified human serum
pseudocholinesterase
was examined in the absence and presence of butyrylcholine iodide, the substrate of
pseudocholinesterase
. Modification by 2-hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide, diethylpyrocarbonate and trinitrobenzenesulfonic acid caused a parallel inactivation of both
pseudocholinesterase
and aryl acylamidase activities that could be prevented by butyrylcholine iodide. With phenylglyoxal and
2,4-pentanedione
as modifiers there was a selective activation of
pseudocholinesterase
alone with no effect on aryl acylamidase. This activation could be prevented by butyrylcholine iodide. N-Ethylmaleimide and p-hydroxy-mercuribenzoate when used for modification did not have any effect on the enzyme activities. The results suggested essential tryptophan, lysine and histidine residues at a common catalytic site for
pseudocholinesterase
and aryl acylamidase and an arginine residue (or residues) exclusively for
pseudocholinesterase
. The use of N-acetylimidazole, tetranitromethane and acetic anhydride as modifiers indicated a biphasic change in both
pseudocholinesterase
and aryl acylamidase activities. At low concentrations of the modifiers a stimulation in activities and at high concentrations an inactivation was observed. Butyrylcholine iodide or propionylcholine chloride selectively protected the inactivation phase without affecting the activation phase. Protection by the substrates at the inactivation phase resulted in not only a reversal of the enzyme inactivation but also an activation. Spectral studies and hydroxylamine treatment showed that tyrosine residues were modified during the activation phase. The results suggested that the modified tyrosine residues responsible for the activation were not involved in the active site of
pseudocholinesterase
or aryl acylamidase and that they were more amenable for modification in comparison to the residues responsible for inactivation. Two reversible inhibitors of
pseudocholinesterase
, namely ethopropazine and imipramine, were used as protectors during modification. Unlike the substrate butyrylcholine iodide, these inhibitors could not protect against the inactivation resulting from modification by 2-hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide and trinitrobenzenesulfonic acid. But they could protect against the activation of
pseudocholinesterase
and aryl acylamidase by low concentrations of N-acetylimidazole and acetic anhydride thereby suggesting that the binding site of these inhibitors involves the non-active-site tyrosine residues.
...
PMID:Chemical modification of the bifunctional human serum pseudocholinesterase. Effect on the pseudocholinesterase and aryl acylamidase activities. 286 42
