<prompt> Final common metabolism of atracurium, mivacurium and succinylcholine are by:ConjugationReductionHydrolysisAcetylation  <response>: Ans: c Hydrolysis Ref: KDT, 6 ed, p.25, 345; Harper 27 ed, p.96The final common pathway in the metabolism of all the three involves hydrolysis by an esterase.The cleavage of a drug molecule by taking up a water molecule; occurs in liver, intestine, plasma and other tissues.E.g.: choline esters, lignocaine, procaine, procainamide, pethidine, oxytocin, atracurium, mivacurium.Atracurium:1 Usually inactivated by spontaneous nonenzymatic degradation Hoffman elimination2 One small fraction is eliminated by hydrolysis by cholinesterase.Mivacurium:Shortest acting competitive blocker, rapidly metabolised by plasma cholinesterases.Succinvlcholine:Shortest acting depolarizing muscle relaxant which is hydrolysed by plasma pseudocholinesterase to succinyl monocholine and then succinic acid and choline.Action lasts only for 3-5 min. It causes phase 2 blockade.Classification of enzymes:A. Oxidoreductases:i Dehydrogenases- removes hydrogen by coenzymes.ii Oxidases- remove H2 and form H2O2.iii Reductases-iv Peroxidases-v Catalasesvi Oxygenase-monooxygenasedioxygenaseB. Transferases:Transfer one group from substrate to another.TransketolaseTransaldolaseKinases transfer phosphate group from ATP to substrateTransaminasePhosphorylaseC. Hydrolases:Cleavage of a molecule by taking up a water molecule1. Phosphatase2. Glycosidases3. EsterasesD. Lyases:Add or remove small molecules like water,ammonia, CO2e.g.:1 decarboxylase2 synthases- ALA synthase.3 aldolase4 fumaraseE. Isomerases:i Epimerasesii Mutasesiii RacemasesF. Ligases:1. Ligation of two molecules at the expense of high energy phosphate bond. eg:synthetases2. CarboxylasesRemember:Carboxylases are ligases but decarboxylases are lyases.Synthetases are ligases but synthases are lyases 