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Chapter 26: Problem 6

Describe the underlying rationale for the regulatory effects exerted on ribonucleotide reductase by ATP, dATP, dTTP, and dGTP.

Short Answer

Expert verified
ATP, dATP, dTTP, and dGTP regulate ribonucleotide reductase, an enzyme essential for DNA synthesis. ATP, as a positive effector, increases the enzyme's activity, signalling high energy levels and the need for increased DNA synthesis. dATP, dTTP, and dGTP, as negative effectors, decrease the enzyme's activity when there is enough of the respective nucleotides, thereby maintaining balance. This regulatory mechanism is a prime example of allosteric regulation.

Step by step solution

01

ATP Understanding

Explain that ATP is a positive effector of ribonucleotide reductase. It means that ATP increases the activity of the enzyme. The underlying rationale of this is that when the cell has high energy (indicated by high levels of ATP), it causes the enzyme to be more active, which leads to an increased DNA synthesis.
02

dATP Understanding

Point out that dATP is a negative effector of ribonucleotide reductase. That is, it decreases the activity of the enzyme. This happens when the cell has enough deoxyadenosine nucleotides (dATP) and no longer needs to synthesize any. This regulation helps maintain balance in the cell.
03

dTTP and dGTP Understanding

Explain that dTTP and dGTP are also negative effectors of ribonucleotide reductase. Their presence signals that the cell has enough of these nucleotides, and there is no need to continue synthesizing them. This regulation ensures balance in the amounts of different types of nucleotides in a cell.
04

Synthesis of The Underlying Rationale

Note that the regulation of ribonucleotide reductase by ATP, dATP, dTTP, and dGTP is an example of allosteric regulation. Here, effector molecules bind to a site on the enzyme distinct from the active site, changing the enzyme's conformation and thereby regulating its activity. This strategy allows cells to control where and when a particular reaction occurs.

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Most popular questions from this chapter

Draw the purine and pyrimidine ring structures, indicating the metabolic source of each atom in the rings.

Write a balanced equation for the conversion of aspartate to fumarate by the purine nucleoside cycle in skeletal muscle.

(Integrates with Chapters \(18-20 \text { and } 22 .)\) By what pathway(s) does the ribose released upon nucleotide degradation enter intermediary metabolism and become converted to cellular energy? How many ATP equivalents can be recovered from one equivalent of ribose?

Illustrate the key points of regulation in (a) the biosynthesis of IMP, AMP, and GMP; (b) \(E .\) coli pyrimidine biosynthesis; and (c) mammalian pyrimidine biosynthesis.

Since dUTP is not a normal component of DNA, why do you suppose ribonucleotide reductase has the capacity to convert UDP to dUDP?
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