Enzymes: Function, definition, and examples - Medical News ...

Enzymes help speed up chemical reactions in the human body. They bind to molecules and alter them in specific ways. They are essential for respiration, ... MedicalNewsTodayHealthConditionsDiscoverToolsConnectSubscribeEnzymes:HowtheyworkandwhattheydoMedicallyreviewedbyElaineK.Luo,M.D.—WrittenbyTimNewmanonJanuary11,2018ThebasicsWhatdoenzymesdo?HowtheyworkTheperfectconditionsCofactorsInhibitionExamplesWeincludeproductswethinkareusefulforourreaders.Ifyoubuythroughlinksonthispage,wemayearnasmallcommission.Here’sourprocess.Enzymeshelpspeedupchemicalreactionsinthehumanbody.Theybindtomoleculesandaltertheminspecificways.Theyareessentialforrespiration,digestingfood,muscleandnervefunction,amongthousandsofotherroles.Inthisarticle,wewillexplainwhatanenzymeis,howitworks,andgivesomecommonexamplesofenzymesinthehumanbody.ThebasicsShareonPinterestTheenzymeamylase(pictured),breaksdownstarchintosugars.Enzymesarebuiltofproteinsfoldedintocomplicatedshapes;theyarepresentthroughoutthebody.Thechemicalreactionsthatkeepusalive–ourmetabolism–relyontheworkthatenzymescarryout.Enzymesspeedup(catalyze)chemicalreactions;insomecases,enzymescanmakeachemicalreactionmillionsoftimesfasterthanitwouldhavebeenwithoutit.Asubstratebindstotheactivesiteofanenzymeandisconvertedintoproducts.Oncetheproductsleavetheactivesite,theenzymeisreadytoattachtoanewsubstrateandrepeattheprocess.Whatdoenzymesdo?Thedigestivesystem–enzymeshelpthebodybreakdownlargercomplexmoleculesintosmallermolecules,suchasglucose,sothatthebodycanusethemasfuel.DNAreplication–eachcellinyourbodycontainsDNA.Eachtimeacelldivides,thatDNAneedstobecopied.EnzymeshelpinthisprocessbyunwindingtheDNAcoilsandcopyingtheinformation.Liverenzymes–theliverbreaksdowntoxinsinthebody.Todothis,itusesarangeofenzymes.HowenzymesworkShareonPinterestEnzymelockandkeymodelThe“lockandkey”modelwasfirstproposedin1894.Inthismodel,anenzyme’sactivesiteisaspecificshape,andonlythesubstratewillfitintoit,likealockandkey.Thismodelhasnowbeenupdatedandiscalledtheinduced-fitmodel.Inthismodel,theactivesitechangesshapeasitinteractswiththesubstrate.Oncethesubstrateisfullylockedinandintheexactposition,thecatalysiscanbegin.TheperfectconditionsEnzymescanonlyworkincertainconditions.Mostenzymesinthehumanbodyworkbestataround37°C–bodytemperature.Atlowertemperatures,theywillstillworkbutmuchmoreslowly.Similarly,enzymescanonlyfunctioninacertainpHrange(acidic/alkaline).Theirpreferencedependsonwheretheyarefoundinthebody.Forinstance,enzymesintheintestinesworkbestat7.5pH,whereasenzymesinthestomachworkbestatpH2becausethestomachismuchmoreacidic.Ifthetemperatureistoohighoriftheenvironmentistooacidicoralkaline,theenzymechangesshape;thisalterstheshapeoftheactivesitesothatsubstratescannotbindtoit–theenzymehasbecomedenatured.CofactorsSomeenzymescannotfunctionunlesstheyhaveaspecificnon-proteinmoleculeattachedtothem.Thesearecalledcofactors.Forinstance,carbonicanhydrase,anenzymethathelpsmaintainthepHofthebody,cannotfunctionunlessitisattachedtoazincion.InhibitionToensurethatthebody’ssystemsworkcorrectly,sometimesenzymesneedtobesloweddown.Forinstance,ifanenzymeismakingtoomuchofaproduct,thereneedstobeawaytoreduceorstopproduction.Enzymes’activitycanbeinhibitedinanumberofways:Competitiveinhibitors–amoleculeblockstheactivesitesothatthesubstratehastocompetewiththeinhibitortoattachtotheenzyme.Non-competitiveinhibitors–amoleculebindstoanenzymesomewhereotherthantheactivesiteandreduceshoweffectivelyitworks.Uncompetitiveinhibitors–theinhibitorbindstotheenzymeandsubstrateaftertheyhaveboundtoeachother.Theproductsleavetheactivesitelesseasily,andthereactionissloweddown.Irreversibleinhibitors–anirreversibleinhibitorbindstoanenzymeandpermanentlyinactivatesit.ExamplesofspecificenzymesTherearethousandsofenzymesinthehumanbody,herearejustafewexamples:Lipases–agroupofenzymesthathelpdigestfatsinthegut.Amylase–helpschangestarchesintosugars.Amylaseisfoundinsaliva.Maltase–alsofoundinsaliva;breaksthesugarmaltoseintoglucose.Maltoseisfoundinfoodssuchaspotatoes,pasta,andbeer.Trypsin–foundinthesmallintestine,breaksproteinsdownintoaminoacids.Lactase–alsofoundinthesmallintestine,breakslactose,thesugarinmilk,intoglucoseandgalactose.Acetylcholinesterase–breaksdowntheneurotransmitteracetylcholineinnervesandmuscles.Helicase–unravelsDNA.DNApolymerase–synthesizeDNAfromdeoxyribonucleotides.InanutshellEnzymesplayahugepartintheday-to-dayrunningofthehumanbody.Bybindingtoandalteringcompounds,theyarevitalfortheproperfunctioningofthedigestivesystem,thenervoussystem,muscles,andmuch,muchmore.LastmedicallyreviewedonJanuary11,2018Biology/BiochemistryGastroIntestinal/Gastroenterology3sourcescollapsedMedicalNewsTodayhasstrictsourcingguidelinesanddrawsonlyfrompeer-reviewedstudies,academicresearchinstitutions,andmedicaljournalsandassociations.Weavoidusingtertiaryreferences.Welinkprimarysources—includingstudies,scientificreferences,andstatistics—withineacharticleandalsolistthemintheresourcessectionatthebottomofourarticles.Youcanlearnmoreabouthowweensureourcontentisaccurateandcurrentbyreadingoureditorialpolicy.Berg,J.M.,Tymoczko,J.L., Stryer,L.(2002).Chapter8.Enzymes:Basicconceptsandkinetics\Enzymes.(n.d.)\Enzymesandtheactivesite.(n.d.)\FEEDBACK:MedicallyreviewedbyElaineK.Luo,M.D.—WrittenbyTimNewmanonJanuary11,2018LatestnewsAlopeciaareata:1in3peopleregrowhairwitharthritisdrugVitaminKmaybehelpfulforpeopleatriskofdementiaTeenmentalhealthinthepandemic:CDCdata‘echoacryforhelp’ScientistsexploreredmarinealgaetotreatfattyliverdiseaseAlzheimer's:Lossofwake-promotingneuronsmayexplainsleepinessRelatedCoverageAnatomyandfunctionofthecolonMedicallyreviewedbySaurabhSethi,M.D.,MPHThecolonispartofthelargeintestine,anditabsorbswaterandnutrientsfromfood.Learnmoreaboutwhatthecolondoesanditsanatomyhere.READMOREAllaboutthecentralnervoussystemMedicallyreviewedbySeungguHan,MDThecentralnervoussystemismadeupofthebrainandspinalcord.Itgathersinformationfromalloverthebodyandcoordinatesactivity.Weexplore…READMOREWhattoknowaboutthequadricepsmusclesMedicallyreviewedbyAmyElizabethWolkin,PT,DPT,MBAWhatistheanatomyandfunctionofthequadricepsmuscles?Readontolearnmoreaboutthismusclegroup,includingcommoninjuriesandstrengthening…READMOREWhattoknowabouttheshoulderWhatdifferentstructuresmakeuptheshoulder?Readontolearnmoreabouttheshoulder,includingitsanatomy,function,andconditionsthatmay…READMOREWhatistheroleofthethumbinhandanatomy?Dopeopleconsiderthethumbtobeafinger?Readontolearnmoreaboutthethumb,suchasitsanatomy,purpose,andconditionsthataffectit.READMORE