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Related Concept Videos

Cholinergic Receptors: Muscarinic01:25

Cholinergic Receptors: Muscarinic

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The pharmacological actions of acetylcholine are elicited via its binding to two families of cholinergic receptors or cholinoceptors, namely, muscarinic and nicotinic receptors. Muscarinic receptors are G protein-coupled receptors and have five subtypes, M1–M5. All mAChR subtypes are activated by acetylcholine and blocked by the antagonist, atropine. 
The subtypes M1, M3, and M5 couple with the Gq subunit and activate the phospholipase C (PLC) activity, mobilizing intracellular Ca2+....
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Cholinergic Antagonists: Chemistry and Structure-Activity Relationship01:29

Cholinergic Antagonists: Chemistry and Structure-Activity Relationship

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Cholinergic antagonists bind to cholinergic receptors and limit the effects of acetylcholine and other cholinergic agonists. Based on the specific cholinergic receptor affinity, these antagonists are classified as muscarinic or nicotinic. Anticholinergics interrupt parasympathetic innervations while sympathetic innervations remain uninterrupted. Muscarinic antagonists are also called 'muscarinic antagonists', 'antimuscarinics', or 'parasympatholytics'. Nicotinic...
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Phase II Reactions: Methylation Reactions01:17

Phase II Reactions: Methylation Reactions

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Methylation is a phase II biotransformation process involving the attachment of a methyl group to a substrate. Enzymes known as methyltransferases orchestrate this reaction.
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
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Biosynthesis of Nucleic Acids01:28

Biosynthesis of Nucleic Acids

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Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. This pathway maintains a balanced nucleotide pool, preventing imbalances that could jeopardize genetic integrity and cellular function. Given the crucial role of nucleotides, their synthesis is tightly regulated to ensure proper cellular homeostasis.Purine BiosynthesisThe biosynthesis of purine nucleotides begins with ribose-5-phosphate, a...
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Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship01:22

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

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Cholinergic agonists or cholinomimetics mimic the action of acetylcholine to stimulate the parasympathetic nervous system. They are categorized into direct-acting and indirect-acting agents. The direct-acting cholinergic drugs induce the parasympathetic response by directly binding to the muscarinic or nicotine receptors. In comparison, the indirect-acting cholinergic drugs prevent acetylcholine hydrolysis, indirectly contributing to the extended parasympathetic response.
The direct-acting...
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Amino Acid Biosynthetic Pathways01:29

Amino Acid Biosynthetic Pathways

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Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which...
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Updated: Apr 24, 2026

Enzymatic Cascade Reactions for the Synthesis of Chiral Amino Alcohols from L-lysine
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Enzymatic Cascade Reactions for the Synthesis of Chiral Amino Alcohols from L-lysine

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A Revised Model for Muscarine Biosynthesis Involving Lysine Trimethylation.

Sebastian Dörner1,2, Kai Rogge1,2, Felix Trottmann3

  • 1Pharmaceutical Microbiology, Friedrich Schiller University Jena, Jena, Germany.

Angewandte Chemie (International Ed. in English)
|April 23, 2026
PubMed
Summary
This summary is machine-generated.

The biosynthesis of the fatal mushroom toxin l-(+)-muscarine originates from l-lysine and l-alanine. This study reveals iterative methylation of l-lysine as the key fungal pathway, distinct from l-carnitine production.

Keywords:
alkaloidbiosynthesismethyltransfermuscarinetoxin

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Last Updated: Apr 24, 2026

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Specificity Analysis of Protein Lysine Methyltransferases Using SPOT Peptide Arrays
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Area of Science:

  • Biochemistry
  • Mycology
  • Toxicology

Background:

  • l-(+)-Muscarine is a dangerous toxin found in mushrooms, posing a significant health risk.
  • The biogenesis of muscarine has been poorly understood since a 1970s study.
  • Collybia rivulosa mushrooms were previously identified as a source of muscarine.

Purpose of the Study:

  • To elucidate the biosynthetic pathway of l-(+)-muscarine.
  • To identify the precursor molecules and key enzymatic steps in muscarine production.
  • To revise the existing model of muscarine biosynthesis.

Main Methods:

  • Stable isotope incorporation experiments using Collybia rivulosa.
  • Extensive mass spectrometric analysis to trace metabolic pathways.
  • Comparison of muscarine biosynthesis with l-carnitine pathways.

Main Results:

  • The backbone of muscarine is assembled from l-lysine and l-alanine.
  • Iterative ε-methylation of l-lysine is the crucial biosynthetic step, producing ε-N,N,N-trimethyl-l-lysine.
  • This specific methylation pathway is unique to muscarine-producing fungi and distinct from l-carnitine biosynthesis.

Conclusions:

  • The study provides unambiguous evidence for the origin of muscarine from l-lysine and l-alanine.
  • A revised biosynthetic model for muscarine is presented, correcting previous assumptions.
  • This research opens avenues for discovering novel, potentially toxic or pharmacologically relevant muscarine-like metabolites.