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Chapter 18: Problem 7

(Integrates with Chapters \(4 \text { and } 14 .)\) How might iodoacetic acid affect the glyceraldehyde- -phosphate dehydrogenase reaction in glycolysis? Justify your answer.

Short Answer

Expert verified
Iodoacetic acid would likely inhibit the GAPDH reaction in glycolysis. This is because the iodoacetic acid will react with the -SH group in the active site of the GAPDH enzyme, which is critical for its function. This action hampers the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate, thus slowing down glycolysis.

Step by step solution

01

Understand the role of iodoacetic acid

Iodoacetic acid is known as an enzyme inhibitor. It often inhibits enzymes by reacting with the -SH (sulfhydryl) groups in the active site of the enzyme. In this case, GAPDH has a cysteine residue in its active site which contains a reactive sulfhydryl group.
02

Understand the GAPDH reaction

GAPDH catalyzes the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate during glycolysis. This process involves oxidation by NAD+ and the attachment of an inorganic phosphate group from the cytosol.
03

Evaluate the impact of iodoacetic acid on the GAPDH reaction

Since iodoacetic acid reacts with the -SH groups often found in enzymes' active sites, and considering the fact that GAPDH has a cysteine residue in its active site with a sulfhydryl group, it's reasonable to infer that iodoacetic acid would inhibit GAPDH activity. As a consequence, the overall process of glycolysis would be slowed down due to a decrease in the conversion rate of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate.

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Most popular questions from this chapter

Fructose bisphosphate aldolase in animal muscle is a class I aldolase, which forms a Schiff base intermediate between substrate (for example, fructose- 1,6 -bisphosphate or dihydroxyacetone phosphate and a lysine at the active site (see Figure 18.12 ). The chemical evidence for this intermediate comes from studies with aldolase and the reducing agent sodium borohydride, \(\mathrm{NaBH}_{4}\). Incubation of the enzyme with dihydroxyacetone phosphate and \(\mathrm{NaBH}_{4}\) inactivates the enzyme. Interestingly, no inactivation is observed if \(\mathrm{NaBH}_{4}\) is added to the enzyme in the absence of substrate. Write a mechanism that explains these observations and provides evidence for the formation of a Schiff base intermediate in the aldolase reaction.

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(Integrates with Chapter 3 .) Enolase catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate \(+\mathrm{H}_{2} \mathrm{O}\). The standard free energy change, \(\Delta G^{\circ},\) for this reaction is \(+1.8 \mathrm{kJ} / \mathrm{mol}\). If the concentration of 2 -phosphoglycerate is \(0.045 \mathrm{m} M\) and the concentration of phosphoenolpyruvate is \(0.034 \mathrm{m} M\), what is \(\Delta G\), the free energy change for the enolase reaction, under these conditions?

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What would be the consequences of a \(\mathrm{Mg}^{2+}\) ion deficiency for the reactions of glycolysis?
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