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Anticholinesterase Agents: Poisoning and Treatment

Anticholinesterase Agents: Poisoning and Treatment

Anticholinesterases, also known as cholinesterase inhibitors, work by blocking the breakdown of acetylcholine, leading to its accumulation in the synaptic cleft. This accumulation indirectly enhances both muscarinic and nicotinic actions. These agents are classified as reversible or irreversible based on their mechanism of action.
Irreversible agents form a strong bond with the cholinesterase enzyme, making it inactive. The breakdown of the phosphorylated enzyme is...

Indirect-Acting Cholinergic Agonists: Mechanism of Action

Indirect-Acting Cholinergic Agonists: Mechanism of Action

Indirect-acting cholinergic agonists work by interacting with an enzyme called acetylcholinesterase (AChE) in the synaptic cleft. They can be reversible or irreversible inhibitors and have different effects on the enzyme.
Reversible inhibitors like edrophonium bind to a specific part of the enzyme called the anionic catalytic site. They form noncovalent bonds, which means they are not strongly attached to the enzyme. This creates a temporary and less stable enzyme–inhibitor complex,...

Catalytically Perfect Enzymes

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.

Most enzymes...

Indirect-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship

Indirect-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship

Indirect-acting cholinergic agonists are agents that interact with the acetylcholinesterase enzyme in the synaptic cleft, preventing the breakdown of acetylcholine into choline and acetate. Consequently, the concentration of acetylcholine in the synaptic cleft increases. These agonists can be classified into reversible and irreversible inhibitors based on their duration of action.
Reversible inhibitors display short to medium durations of action. Short-acting agents include simple alcohols with...

ortho–para-Directing Activators: –CH3, –OH, –&NoBreak;NH2, –OCH3

ortho–para-Directing Activators: –CH₃, –OH, –⁠NH₂, –OCH₃

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

Sharpless Epoxidation

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The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...

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Related Experiment Video

Updated: Jun 12, 2025

Multi-enzyme Screening Using a High-throughput Genetic Enzyme Screening System

Multi-enzyme Screening Using a High-throughput Genetic Enzyme Screening System

Published on: August 8, 2016

Supercharged Phosphotriesterase for improved Paraoxon activity.

Jacob Kronenberg¹, Dustin Britton¹, Leif Halvorsen²

¹Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering, Brooklyn, New York 11201, USA.

Protein Engineering, Design & Selection : PEDS

|September 18, 2024

Summary

Supercharging improved phosphotriesterases (PTEs) for neutralizing organophosphates (OPs). A negatively supercharged PTE variant showed enhanced catalytic activity, while a positively supercharged variant did not, informing future enzyme engineering.

Keywords:

Protein engineering enzyme engineering organophosphates phosphotriesterase supercharging

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Chemical Triphosphorylation of Oligonucleotides

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Last Updated: Jun 12, 2025

Multi-enzyme Screening Using a High-throughput Genetic Enzyme Screening System

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Expression and Purification of Nuclease-Free Oxygen Scavenger Protocatechuate 3,4-Dioxygenase

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Published on: June 2, 2022

Area of Science:

Biochemistry
Protein Engineering
Enzyme Catalysis

Background:

Phosphotriesterases (PTEs) neutralize toxic organophosphates (OPs).
PTEs exhibit limited thermostability and solubility, hindering their application.
Protein supercharging enhances protein solubility and thermostability via surface charge mutations.

Purpose of the Study:

To engineer improved PTE variants using computational supercharging.
To assess the impact of supercharging on PTEs' thermodynamic stability and catalytic activity against OPs.

Main Methods:

Employed a computational protein supercharging algorithm (Rosetta).
Generated and characterized negatively and positively supercharged PTE variants.
Assessed thermodynamic stability and catalytic efficiency across a temperature range (25°C-55°C).

Main Results:

A negatively supercharged PTE variant (+12 net charge) exhibited increased catalytic activity from 25°C to 55°C with comparable thermostability.
A positively supercharged PTE variant (-14 net charge) showed reduced thermostability and catalytic efficiency.
Supercharging effects on PTEs varied significantly with charge direction.

Conclusions:

Negative supercharging is a viable strategy for enhancing PTE catalytic efficiency.
This study provides insights into designing thermostable and highly active PTEs for organophosphate detoxification.
Findings guide future enzyme engineering efforts for improved biocatalysts.