Term
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Definition
| enzymes that follow Michaelis-Menten kinetics |
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Term
| how Michaelis-Menten enzyme action is governed |
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Definition
| simply by mass action; they catalyze when substrate is present |
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Term
| the type of enzymes most enzymes in the cell are |
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Definition
| Michaelis-Menten enzymes; not regulated in the cell |
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Term
| an effective way to regulate metabolic traffic |
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Definition
| regulating enzyme activity |
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Term
| the enzymes that regulate metabolic traffic |
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Definition
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Term
| key features of allosteric enzymes |
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Definition
-regulation of catalytic activity by environmental signals
-kinetics more complex than those of Michaelis-Menten enzymes
-quaternary structure with multiple active sites in each enzyme |
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Term
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Definition
| seems to be the step after which the rxn that yields the final product will take place |
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Term
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Definition
| seems to be the final product of a pathway binding reversibly to the committed step to inhibit the rxn |
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Term
| depiction of feedback inhibition |
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Definition
[image]
here, the final product binds to an alternate site on the allosteric enzyme to inhibit the committed step |
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Term
| enzymes that catalyze the committed step of metabolic pathways |
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Definition
| allosteric enzymes always do this |
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Term
| some molecules allosteric enzymes can recognize to regulate production of the final product |
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Definition
-inhibitor molecules
-stimulatory molecules |
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Term
| depiction of a pathway that uses both inhibition and stimulation |
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Definition
[image]
here, F and I stimulate the production of each other, F inhibits production of itself, I inhibits production of itself, and K inhibits production of both F and I, thus inhibiting production of itself |
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Term
| how allosteric enzymes are regulated |
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Definition
-changes in substrate concentration
-other molecules, i.e., non-substrate molecules |
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Term
| how Michaelis-Menten enzymes and allosteric enzymes differ in kinetics |
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Definition
[image]
the curve for allosteric is sigmoidal because it resembles the letter S |
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Term
| 2 properties unique to allosteric enzymes |
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Definition
1: regulation of catalytic activity
2: sigmoidal kinetics |
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Term
| the kinetics of allosteric enzymes |
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Definition
| sigmoidal (resembles S on a graph) |
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Term
| the concerted model or MWC model of allosteric enzyme regulation |
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Definition
based on several premises
-allosteric enzymes have multiple active sites on different polypeptide chains
-the enzyme can exist in the R (relaxed, more active) or T (tense, less active) conformation state
-all subunits or active sites must be in the same state; no hybrids (this is the symmetry rule)
-substrate (S) binds more readily with R form than T form |
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Term
| the active sites on allosteric enzymes |
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Definition
| have multiple active sites on different polypeptide chains |
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Term
| the 2 conformations or states an allosteric enzyme can be in |
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Definition
-R (relaxed, active)
-T (tense, less active) |
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Term
| state of allosteric enzyme when there's no substrate |
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Definition
| R and T states in e'librium, with T being more stable and thus more common |
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Term
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Definition
| the t/r ratio, which is in the hundreds when there's no substrate |
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Term
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Definition
| rule that all the subunits or active sites of an allosteric enzyme be in the same state |
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Term
| the form of allosteric enzyme substrates more readily bind to |
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Definition
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Term
| why allosteric enzymes have sigmoidal (S-shaped) kinetics |
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Definition
| because the binding of substrate disrupts the T <--> R e'librium in favor of R |
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Term
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Definition
accumulation of substrate binding and disrupting the T <--> R e'librium in favor of R
this accounts for the sharp increase in velocity of rxn |
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Term
| the physiological significance of cooperativity in allosteric enzymes (accumulation of substrate binding and disrupting the T <--> R e'librium in favor of R) |
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Definition
| allosteric enzymes are more sensitive to changes in substrate concentration near KM than Michaelis-Menten enzymes with the same Vmax |
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Term
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Definition
| rapid increase in enzyme activity above a certain threshold |
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Term
| how the T <--> R e'librium of allosteric enzymes is regulated |
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Definition
| regulator molecules, such as positive and negative effectors |
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Term
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Definition
binds to the R form of an allosteric enzyme at a regulatory site, distinct from the active site, to stabilize it, increasing c'tration of R and making that enzyme more likely to bind with substrate
make allosteric enzyme more sensitive to substrate |
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Term
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Definition
binds to T form of an allosteric enzyme and stabilizes it, increasing c'tration of T, which makes the R form less likely to bind with substrate
make allosteric enzyme less sensitive to substrate |
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Term
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Definition
| effects of regulatory molecules on allosteric enzymes |
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Term
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Definition
| effects of substrates on allosteric enzymes |
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Term
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Definition
| the binding of substrate to one site of the allosteric enzyme influencing substrate binding to the neighboring sites without necessarily inducing a transition encompassing the entire enzyme |
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Term
| depiction of sequential model |
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Definition
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Term
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Definition
| the binding of one substrate decreasing the affinity of other sites on an allosteric enzyme for the substrate |
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Term
| the model many allosteric enzymes follow |
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Definition
| some combination of the concerted and sequential model |
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