ENZYMESENZYMES definitionEnzymes are highly selective (specific for substrate), macromolecular, biological catalysts synthesised by living cells for the acceleration of metabolic reactions.Chemically, enzymes are mostly globular proteins (eception!Ribozyme is made of "N#).$hey are colloidal and thermo labile in nature.$hey increase the rate of thermodynamically feasible reactions, primarily by lo%erin& the acti'ation ener&y, so that e(uilibrium state is attained (uic)ly. $hey do not alter the e(uilibrium of a chemical reaction. $hey do not &et consumed or altered after a chemical reaction.C*#SS+,+C#$+-N -, ENZYMESEnzymes are &rouped into . ma/or classes based on the type of reactions they catalyze0 (-$1*+*)Oxidoreductases: catalyze the transfer of oy&en, hydro&en or electrons from one substrate to another2 i.e, oidisin&3reducin& a substrate by simultaneously reducin&3oidisin& another substrate3coenzyme.e.&. #lcohol dehydro&enase0 #lcohol!N#4!oidoreductase, cytochrome oidaserans!erases: catalyze the transfer of &roups other than hydro&en or oy&en bet%een substrates.E.&. 1eo)inase 0 #$5!1eose!.!phosphate!transferase, transaminases, phosphorylases"ydrolases: catalyze the hydrolysis of ester, ether, peptide or &lycosidic bonds by addin& %ater.e.&. *ipase0 ($riacyl&lycerol acyl hydrolase), acetylcholine esterase, pepsin, urease, phospahatases#yases: catalyze the addition3remo'al of functional &roups from substrates or brea) bondsby mechanism other than hydrolysis.e.&. #ldolase0 ()etose 6phosphate aldehyde lyase), fumarase, decarboylases$somerases: catalyze the formation of optical, &eometric or positional isomers of substrate.E.&. $riose phosphate isomerise0 (&lyceraldehyde 7!phosphate )etoisomerase), retinol isomerase, racemases, epimerases, cis!trans isomerases.#igases: catalyse synthetic reactions, %here substrates are lin)ed to&ether %ith simultaneous hydrolysis of #$5.e.&. &lutamine synthetase, carbamoyl phosphate synthetase, acetyl Co.# carboylase+N$"#CE**8*#" #N4 E9$"#CE**8*#" ENZYMESZYM-:ENS;+,8NC$+-N#* ENZYMES #N4 M8*$+5*E ENZYME C-M5*E9ESC-,#C$-"S # cofactor is a non!protein compound that enhances or potentiates an enzyme