A steric blockade model for inhibition of acetylcholinesterase by peripheral site ligands and substrate.

@article{Rosenberry1999ASB,
  title={A steric blockade model for inhibition of acetylcholinesterase by peripheral site ligands and substrate.},
  author={T. Rosenberry and W. Mallender and P. Thomas and T. Szegletes},
  journal={Chemico-biological interactions},
  year={1999},
  volume={119-120},
  pages={
          85-97
        }
}
The active site gorge of acetylcholinesterase (AChE) contains two sites of ligand binding, an acylation site near the base of the gorge and a peripheral site at its mouth. We recently introduced a steric blockade model which demonstrated that small peripheral site ligands like propidium can inhibit substrate hydrolysis simply by decreasing the substrate association and dissociation rate constants without altering the equilibrium constant for substrate binding to the acylation site. We now… Expand
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TLDR
It is shown that cationic substrates such as acetylthiocholine and 7-acetoxy-N-methylquinolinium (M7A) bind to the peripheral site as well as to the acylation site, which indicates that the primary physiologic role of the AChE peripheral site is to accelerate the hydrolysis of acetylcholine at low substrate concentrations. Expand
Nonequilibrium analysis alters the mechanistic interpretation of inhibition of acetylcholinesterase by peripheral site ligands.
TLDR
An alternative nonequilibrium analysis of the steady-state inhibition patterns of the active site gorge of acetylcholinesterase is introduced, which concludes that this model can account for the inhibition of AChE by small peripheral site ligands such as propidium without invoking any conformational interaction between the peripheral and acylation sites. Expand
Fasciculin 2 Binds to the Peripheral Site on Acetylcholinesterase and Inhibits Substrate Hydrolysis by Slowing a Step Involving Proton Transfer during Enzyme Acylation (*)
TLDR
The association and dissociation rate constants for fasciculin 2 interaction with the human enzyme in the presence of ligands that bind to either the peripheral site or the acylation site are reported, confirming that propidium is strictly competitive with fascicul 2 for binding to the peripheralsite and indicating that steps involving proton transfer during enzyme acylations are slowed. Expand
Binding of the neurotoxin fasciculin 2 to the acetylcholinesterase peripheral site drastically reduces the association and dissociation rate constants for N-methylacridinium binding to the active site.
TLDR
Estimates of total AChE concentrations, KL, or KL' from analyses of relaxation amplitudes agreed well with those from equilibrium fluorescence, confirming that the relaxations corresponded to the bimolecular reactions of interest. Expand
Role of the peripheral anionic site on acetylcholinesterase: inhibition by substrates and coumarin derivatives.
TLDR
Evidence is presented that competition with propidium obtained by direct fluorescence titrations, when combined with inhibition kinetics, provides a more reliable means for ascertaining site selectivity of various inhibitors than does a kinetic analysis alone. Expand
Organophosphorylation of Acetylcholinesterase in the Presence of Peripheral Site Ligands
TLDR
In contrast, the binding of the polypeptide neurotoxin fasciculin to the peripheral site of AChE dramatically decreased phosphorylation rate constants, suggesting that molecular or electronic strain caused by the proximity of propidium to EMPC in the ternary complex may promoteosphorylation. Expand
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TLDR
Although propidium and edrophonium associate at separate sites on acetylcholinesterase, bis-quaternary ligands where the quaternary nitrogens are separated by 14 A displace both ligands from the enzyme with equal effectiveness. Expand
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T theoretical equations were derived for an enzyme with two binding sites to both of which substrate and inhibitor can combine, and it was shown that haloxon combines with a site involved in inhibition by substrate. Expand
Binding of 125I-fasciculin to rat brain acetylcholinesterase. The complex still binds diisopropyl fluorophosphate.
TLDR
It is demonstrated that fasciculins bind on a peripheral site of AChE, distinct from the catalytic site and, at least partly, common with the sites on which some cationic inhibitors and the substrate in excess bind. Expand
Spectrophotometric study of the acetylcholinesterase-catalyzed hydrolysis of 1-methyl-acetoxyquinolinium iodides.
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TLDR
Spectrophotometric procedures were used to study the acetylcholinesterase-catalyzed hydrolysis of a series of isomeric 1-methyl-acetoxyquinolinium iodides, and a sensitive method was developed for determination of quantities of enzyme as low as 0.005 unit. Expand
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