Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 19: Problem 3

(Integrates with Chapter \(15 .\) ) The serine residue of isocitrate dehydrogenase that is phosphorylated by protein kinase lies within the active site of the enzyme. This situation contrasts with most other examples of covalent modification by protein phosphorylation, where the phosphorylation occurs at a site remote from the active site. What direct effect do you think such active-site phosphorylation might have on the catalytic activity of isocitrate dehydrogenase? (See Barford, D., 1991. Molecular mechanisms for the control of enzymic activity by protein phosphorylation. Biochimica et Biophysica Acta \(1133: 55-62 .\)

Short Answer

Expert verified
Active-site phosphorylation of isocitrate dehydrogenase could directly impact the enzyme's catalytic activity. Given that the active site is where the substrate binds to the enzyme, modifications here could prevent or enhance substrate binding. Therefore, the phosphorylation could either inhibit or increase the ability of the enzyme to catalyze its reaction.

Step by step solution

01

Understand Phosphorylation and Its Purpose

Phosphorylation is the process where a phosphate group is added to a molecule by a protein kinase. This can serve as an 'on' or 'off' switch for many proteins, including enzymes, by changing their conformation (shape), and hence, their activity.
02

Understand Active-Site Phosphorylation

In active-site phosphorylation, the phosphate group is added to a specific location the active site where the substrate molecule binds itself. This change could alter the enzyme's shape in a way that the substrate can no longer bind. It could either inhibit or enhance the enzyme's ability to catalyze a reaction.
03

Apply Knowledge to Isocitrate Dehydrogenase

In the case of isocitrate dehydrogenase, phosphorylation at the active site would directly impact the enzyme's ability to catalyze its reaction. This is because the active site is the exact location where the substrate binds, and so, modifications here could directly prevent or enhance substrate binding. Thus, this active-site phosphorylation would directly modify the enzyme's catalytic activity.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Aconitase is rapidly inactivated by \(2 R, 3 R\) -fluorocitrate, which is produced from fluoroacetate in the citrate synthase reaction. Interestingly, inactivation by fluorocitrate is accompanied by stoichiometric release of fluoride ion (i.e., one F-ion is lost per aconitase active site \() .\) This observation is consistent with "mechanism-based inactivation" of aconitase by fluorocitrate. Suggest a mechanism for this inactivation, based on formation of 4 -hydroxy-trans-aconitate, which remains tightly bound at the active site. To assess your answer, consult this reference: Lauble, H., Kennedy, M., et al., 1996. The reaction of fluorocitrate with aconitase and the crystal structure of the enzyme-inhibitor complex. Proceedings of the National Academy of Sciences \(93: 13699-13703\)

In addition to fluoroacetate, consider whether other analogs of TCA cycle metabolites or intermediates might be introduced to inhibit other, specific reactions of the cycle. Explain your reasoning.

Based on the action of thiamine pyrophosphate in catalysis of the pyruvate dehydrogenase reaction, suggest a suitable chemical mechanism for the pyruvate decarboxylase reaction in yeast: Pyruvate \(\longrightarrow\) acetaldehyde \(+\mathrm{CO}_{2}\)

(Integrates with Chapter 3 .) Aconitase catalyzes the citric acid cycle reaction: Citrate \(\rightleftharpoons\) isocitrate The standard free energy change, \(\Delta G^{\circ \prime}\), for this reaction is +6.7 \(\mathrm{kJ} / \mathrm{mol}\). However, the observed free energy change \((\Delta G)\) for this reaction in pig heart mitochondria is \(+0.8 \mathrm{kJ} / \mathrm{mol}\). What is the ratio of [isocitrate]/[citrate] in these mitochondria? If [isocitrate] = \(0.03 \mathrm{m} M,\) what is [citrate]?

Describe the labeling pattern that would result in the glyoxylate cycle if a plant were fed acetyl-CoA labeled at the \(-\mathrm{CH}_{3}\) carbon.
See all solutions

Recommended explanations on Chemistry Textbooks

Nuclear Chemistry

Read Explanation

Organic Chemistry

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Chemical Analysis

Read Explanation

Chemistry Branches

Read Explanation

Chemical Reactions

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free