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nhb

2. Relationship between substrate concentration and the rate
of an enzyme-catalysedreaction
rectangular
hyperbola
Maximal velocity (Vmax)
Maximum reaction rate (v
observed at saturating
substrate
concentrations) for a given
concentration of enzyme:
Vmax=¼ kcat[E]t.

3. Michael-MentonEquation

4. Michael-MentonEquation
Plotting in the form of y = m(x) + C

5. Lineweaver-Burk Plot

6. Inhibitors
Somesubstancesreduceorevenstopthecatalyticactivityofenzymesin
biochemicalreactions.Theyblockordistorttheactivesite.Thesechemicals
arecalledinhibitors,becausetheyinhibitreaction.
Inhibitorsthatoccupytheactivesiteandpreventasubstratemoleculefrom
bindingtotheenzymearesaidtobeactivesite-directed(orcompetitive,as
they'compete'withthesubstratefortheactivesite).
Inhibitorsthatattachtootherpartsoftheenzymemolecule,perhaps
distortingitsshape,aresaidtobenon-activesite-directed(ornon
competitive)

7. Reversibleandirreversibleinhibitorsarechemicalswhichbindtoan
enzymetosuppressitsactivity.Onemethodtoaccomplishthisistoalmost
permanentlybindtoanenzyme.Thesetypesofinhibitorsarecalled
irreversible.However,otherchemicalscantransientlybindtoanenzyme.
Thesearecalledreversible.Reversibleinhibitorseitherbindtoanactivesite
(competitiveinhibitors),ortoanothersiteontheenzyme(non-competitive
inhibitors).(TeachMePhysiology,2022)
_____________________________________________
TeachMePhysiology,2022.EnzymeInhibition
https://teachmephysiology.com/biochemistry/molecules-and-signalling/enzyme-inhibition/

8. CompetitiveInhibition
DuringCI,Theinhibitor(I)competeswiththesubstrate(S)forthe
enzymeactivesite(alsoknownastheS-bindingsite).Bindingofeitherof
thesemoleculesintheactivesiteisamutuallyexclusiveevent.
•Thesubstrateandinhibitorshareahighdegreeofstructuralsimilarity.
However,theinhibitorcannotproceedthroughthereactiontoproduce
product.
•Increasingtheconcentrationofsubstratewilloutcompetetheinhibitorfor
bindingtotheenzymeactivesite
•Acompetitivereversibleinhibitorcanbeidentifiedbyitscharacteristic
effectsuponkineticdata

9. CompetitiveInhibition
Competitiveinhibitorscompetewiththesubstrateattheactivesite,and
thereforeincreaseKm(theMichaelis-Mentenconstant).However,Vmaxis
unchangedbecause,withenoughsubstrateconcentration,thereactioncan
stillcomplete.Thegraphplotofenzymeactivityagainstsubstrate
concentrationwouldbeshiftedtotherightduetotheincreaseoftheKm,
whilsttheLineweaver-Burkeplotwouldbesteeperwhencomparedwith
noinhibitor.

10. CompetitiveInhibition
TheexpressionfortheMichaelis-Mentenexpressioninthepresenceof
areversiblecompetitiveinhibitoris:

11. CompetitiveInhibition

12. CompetitiveInhibition
Inhibitorresemblesthesubstrateandthuscompeteswithitforthe
bindingsiteattheactivecenteroftheenzyme.Inhibitorbindsatthe
activecenter,blockingthesubstratefrominteractingwiththebinding
site.
Inhibitorcanbeovercomethroughanexcessofthesubstrate
;therefore,thisinhibitionisreversible.
Decreasesaffinityoftheenzymeforthesubstrate
Asaffinitydecreases,theKmvalueincreases,sinceanincreased
Substrateconcentrationisrequiredtoobtainthehalf-maximalvelocity.
Vmaxisnotchanged,however.(Lecturio,2022)
_____________________________________________
Lecturio,2022
https://www.lecturio.com/concepts/enzyme-inhibition/

13. Competitive
Inhibition
(Lecturio,2022)

14. Competitive
Inhibition
(Lecturio,2022)

15. Comparisonbetweeninhibitors
(TeachmePhysiology, 2022)

16. Competitiveinhibitionisusuallycausedbysubstancesthatarestructurally
relatedtothesubstrate,andthuscombineatthesamebindingsiteasthe
substrate.Thebindingsareexclusivetoeachother,formingeitheran
enzyme–substrate(ES)oranenzyme–inhibitor(EI)complexbutnota
ternarycomplex(EIS)
Thistypeofinhibitioncanbecompletelyovercomebyhighsubstrate
concentrationsandthusdoesnotaffecttheV.TheKmisincreasedbya
factorof(1+[I]/Ki).(Pharmacology,2009)
______________________________________
Pharmacology,2009.CompetitiveInhibition.
https://www.sciencedirect.com/topics/medicine-and-dentistry/competitive-inhibition
Hyone-MyongEun,inEnzymologyPrimerforRecombinantDNATechnology,1996