L2i: Cholinesterases

  • 2 enzymes
    1. Similar structure
    2. Differ in location, substrate & function

1) Acetylcholinesterase

  • Aka: true cholinesterase
  • Location: all cholinergic junctions
  • Substrate: ACh

2) Butyrylcholinesterase

    • Aka: pseudocholinesterase
    • Location: Liver, skin, GI smooth m., kidneys, brain & insoluble in plasma (PLASMA CHOLINESTERASE)
    • Substrate: Butyrylcholine, ACh (fav less rapidly cf. ↑), sux, mivacurium, ester Las, diamorphine, aspirin

NB: Renin & esmolol are not metabolised by Butyrylcholinesterase. They are metabolised by NON-SPECIFIC CHOLINESTERASES

    • Each Acetylcholinesterase has 6 active sites
    • Each active site: ANIONIC SITE & ESTERATIC SITE
Anionic Site
    • ACh → hydrolysed by AChE → Acetic acid

NB: 10,000 ACh molecules hydrolysed per second