You’ve isolated a novel enzyme, Sadase, that cleaves the substrate Sad into the
ID: 224400 • Letter: Y
Question
You’ve isolated a novel enzyme, Sadase, that cleaves the substrate Sad into the product Happy. During your study, you isolate two ligands, Schule and Lehrer. Happy produces a strong signal at 531 nm and you isolate the following data looking at the change in absorbance in 21 seconds with increasing concentrations of Sad: [Sad] V(1) (Sadase) V(2) (Sadase + Schule) V(3) (Sadase + Lehrer) 1 0.19 0.105 0.151 5 0.419 0.222 0.366 15 0.483 0.273 0.469 30 0.522 0.288 0.522 45 0.513 0.299 0.515 a. Determine if these ligands are positive or negative regulators. Additionally, determine the type of inhibition for any negative regulators. Be sure to clearly show your analysis and explain your rationale. No credit will be given for answers without explanation. (20 points) b. Comment on the possible structural similarities between the substrate and the two inhibitors. (5 points)
Explanation / Answer
Negative regulators will inhibit the product formation and positive regulator will favor the product formation. So V3 is favoring the product (Happy) formation so the absorbance is higher than V1 (Sadase alone). But V2 is inhibiting the product formation so the absorbance is lower than V1.
Ligand in V3 acts as positive regulator but the ligand in V2 acts as negative regulator.
Ligand in V2 acts as competitive inhibitor which does not allow the substrate to bind the enzyme so the product formation will be less. Ligand in V3 acts as non-competitive inhibitor that is binding of this ligand does not hinder the binding of substrate and product formation.
Ligand in V2 is structurally similar to substrate so it acts as competitive inhibitor. But ligand in V3 is not so similar to substrate so it acts as non-competitive inhibitor.
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