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24 Cards in this Set
- Front
- Back
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Acetylcholinesterase
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- preferred substrace: Ach
- activity towards acetyl-B-methylcholine - no activity towrds succinylcholine or benzoylcholine - recovery by pralidoxime - located in neurons, muscles and erythrocytes - vital physiological need - bound to BM - FAST turnover rate |
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Butyrylcholinesterase
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- preferred substrate: butyrylcholine
- activity towards succinylcholine and benzoylcholine - no activity towards acetyl-B-bethylcholine - no recovery from pralidoxime - located in plasma, liver, muscle and brain - not a vital enzyme |
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Pralidoxime
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- reactivate AChE after expusure to toxic organophosphate nerver agents/pesticides
- nucleophilic --> attack and displace the phosphoryl group from it's attachment --> displace OP from catalytic site |
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types of AChE's
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Reversible:
- Quaternary amines - carbamates Irreversible: - Organophosphates |
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Quaternary amines
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- AChE
- Rapidly reversible - do not bind ChE covalently - bind either peripheral anionic site or hydrophobic region of catalytic site - ex: edrophonium and decamethonium |
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Carbamates
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- Reversible AChE
- Reacts with ChE in same way as Ach (acylation) but recovery of enzyme from acylation is slow |
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Edrophonium
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- Quaternary amine - AChE
- Use for DIAGNOSIS of MG (very short acting) |
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Organophosphates
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- bind ChE via acylation, but very resistant to deacylation (days) --> irreversib;e
- used in insecticides and nerve poisons |
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Physostigmine
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- Carbamate AChE
- Tertiary amine - Lipid soluble --> well absorbed/BBB - Used for: Narrow angle GLAUCOMA - Increase ach --> allow for further drainage - Used with muscarinic agonists, B-adrenergic antagonists, diuretics and epi - given in atropine overdose (both can cross BBB) |
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Neostigmine
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- Charged carbamate
Uses: - Paralytic Ileus and atony of urinary bladder - Myasthenia Gravis - Recovery of NM block following surgery (also give antimuscarinic to prevent PS muscarinic response) - given for curare/nicotinic receptor agonist poisoning -- dont cross BBB - Nonselective action therefore use limited - Selectivity is obtained by localized application (ie. Directly to eye) |
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Tacrine
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- acridine AChE
- lipophilic - cross BBB - Used for Alzheimer's (degeneration of cholinergic neurons) - slow the rate of cognitive degeneration |
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Velnacrine
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- acridine AChE
- lipophilic - cross BBB - Used for Alzheimer's (degeneration of cholinergic neurons) - slow the rate of cognitive degeneration |
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Diazinon
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- OP insecticide (AChE)
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Malathion
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- OP pesticide once activated (AChE)
- Less toxicity to humans than other OPs - Metabolized slowly in insects so still towic in them |
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methylparathion
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- OP pesticide once activated (AChE)
- Controlled use in agriculture as insecticide |
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Chloropyrifos
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- OP insecticide (AChE)
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Carbaryl
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- Carbamate insecticide (AChE)
- Less potent and toxic than OPs |
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Soman
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- Nerve gase
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Sarin
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- Nerve gase
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VX
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- Nerve gase
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Pesticides
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- Both OP and carbamates
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OP toxicity
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- diaphoresis
- Bradycardia/hypotension - treat with atropine and respiratory support Cholinesterase Inhibitor poisoning DUMBBELSS Diarrhea, Urination, Miosis, Brochospasm, Bradycardia, Excitation of Skeletal Muscle and CNS, Lacrimation, Sweating, Salivation (also abdominal cramping) |
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Nerve Gas
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- most toxic AChE's known
- Very potent OPs - Cause ChE's to age rapidly so they cannot be reactivated by oximes |
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Nerve Gas Treatment
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- DECONTAMINATION
- respiratory support - repeated injections of atropine and oximes - working on prophylactic treatment for military |
