Term
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Definition
| transfer of electrons (hydride ions or H atoms) |
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Term
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Definition
group transfer reactions
ex: kinase - transfers phosphate groups |
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Term
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Definition
| hydrolysis reactions (transfer of functional groups to water) |
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Term
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Definition
| addition of groups to double bond, or formation of double bonds by removal of groups |
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Term
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Definition
| transfer of groups within molecules to yield isomeric forms |
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Term
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Definition
| formations of c-c, c-s, c-o, and c-n bonds by condensation reactions coupled to cleavage of ATP or similar cofactors |
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Term
Michaelis-Menton steady state kinetics
vo |
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Definition
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Term
| Key Michaelis-Menton steady state assumptions |
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Definition
Formation of ES complex
Rate of formation and breakdown are =
Initial rate of reaction (dP/dt) is linear before P accumulates |
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Term
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Definition
x axis: 1/[s] (1/molarity)
y axis: 1/[v] (1/molarity per time) |
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Term
| x intercept on lineweaver burke plot |
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Definition
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Term
| y intercept on lineweaver burke plot |
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Definition
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Term
| Limitations of Lineweaver Burke Interpretation |
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Definition
| small errors in measuring Vo at varying [S] translate to large errors in Vmax and Km |
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Term
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Definition
[S] at 1/2 Vmax
Ratio of the rate of dissociation to the rate of association |
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Term
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Definition
K2 + K-1 / K1
~K-1/K1 if K2 is small |
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Term
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Definition
means that K1 is large - lots of association between E and S
HIGH AFFINITY |
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Term
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Definition
| rate of reaction when all enzyme molecules are fully saturated |
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Term
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Definition
K2[ET]
because [ES] = [ET] |
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Term
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Definition
turnover number
rate f=of substrate converted to product when enzyme is fully saturated with enzyme
= Vmax/[ET] |
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Term
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Definition
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Term
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Definition
Kcat/Km
turnover number over ratio of dissoc. to assoc. |
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Term
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Definition
shows how often enzyme and substrate contact each other and MEASURE OF CATALYTIC EFFICIENCY
depends on: affinity&rate of catalysis |
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Term
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Definition
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Term
| How do enzyme inhibitors reduce reaction rate? |
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Definition
interfere with substrate binding
interfere with turnover |
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Term
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Definition
associate and dissociate rapidly from enzyme
temporarily inhibition just to regulate
common
ex: phosphodiesterase 5 inhibitor (sildenafil); increases cGMP |
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Term
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Definition
dissociate very slowly
most drugs |
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Term
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Definition
competes with S for AS
Resembles S, but unreactive |
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Term
| when does a competitive inhibitor stop working |
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Definition
| when it had diffused out of the AS |
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Term
| how do you overcome a competitive inhibitor |
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Definition
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Term
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Definition
| Inhibitor can only bind to [ES] - does not prevent substrate binding, does not bind at AS |
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Term
| Can increasing [S] compensate for an uncompetitive inhibitor? |
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Definition
| NO - more substrate would make more ES complexes, which is what the I binds to |
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Term
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Definition
HAS A DISTINCT BIND SITE SOMEWHERE OTHER THAN THE AS
DOES NOT INTERFERE WITH SUBSTRATE BINDING |
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Term
| KINETICS of Competitive I |
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Definition
No change in Vmax
Km increases |
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Term
| KINETICS of Competitive I - Lineweaver Burke Plot |
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Definition
y intercept doesn't move
x intercept less negative (Km larger, reciprocal smaller) - steeper line |
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Term
| KINETICS of Uncompetitive Inhibitors |
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Definition
Vmax decreases ([S] can't help)
Km appears to decrease...
same slope (Km/Vmax) |
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Term
| KINETICS of Uncompetitive I - Lineweaver Burke plot consequenes |
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Definition
Vmax smaller - yint increases
Km appears to decrease - xint larger (more neg) |
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Term
| KINETICS of mixed inhibitors |
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Definition
Vmax decreases
Km may not change (NO CHANGE IF INHIBITOR DOES NOT CHANGE SUBSTRATE BINDING) but apparent increase because of potential [E] binding |
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Term
| KINETICS of Mixed Inhibitors - Lineweaver Burke plot consequences |
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Definition
Y int larger
X int may stay the same |
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Term
| Why does Km appear to decrease when an uncompetitive inhibitor is applied? |
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Definition
| because an uncompetitive inhibitor renders ES useless by forming the non functional ESI complex, less S is being bound by E. Less S is required to reach Vmax. Km decreases. -1/Km decreases. X-int shifts left - more negative |
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Term
| non michaelis menton kinetics |
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Definition
curves of [S] vs V are sigmoidal
ex: Allosteric enzymes |
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Term
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Definition
usually multisubunit
multiple active sites
regulate multi-step pathways |
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