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Question #44981

Difficulty: 8/10 | 🟢 Free

The Question

An enzyme, Uridine nucleosidase, specifically catalyzes the hydrolysis of the N-glycosidic linkage in Uridine to yield uracil and D-ribose at $298\text{ K}$ and $\text{pH } 7.4$ . A researcher hypothesizes that Uridine-5'-monophosphate (UMP) will act as a strong competitive inhibitor for this enzyme due to its structural similarity to Uridine. Consider the following statements regarding this system:

I. The N-glycosidic linkage hydrolyzed by the enzyme in Uridine is a $\beta$ -linkage. II. UMP will effectively bind to the active site and significantly increase the apparent $K_m$ of the enzyme for Uridine without altering $V_{max}$ . III. The 5'-phosphate group of UMP exists predominantly as a dianion at $\text{pH } 7.4$ , causing severe electrostatic repulsion and steric hindrance at the active site. IV. The 'Lock and Key' specificity of the enzyme relies on the unhindered, neutral 5'-OH group of the ribofuranose ring for proper active site fit.

How many of the above statements are correct?

Options

A.
1
B.
2
C.
3
D.
4

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Nucleoside vs Nucleotide|Enzyme Specificity 'Lock and Key'|Glycosidic Linkage Geometry

Why This Question Is Tricky

Common Mistakes

The question tests the student's ability to differentiate between nucleosides and nucleotides and apply this structural difference to enzyme kinetics and the 'Lock and Key' model.

A common trap is assuming that structural similarity (sharing the base and sugar) automatically makes a molecule a competitive inhibitor.

Students often overlook the profound steric and electrostatic impact of the 5'-phosphate group at physiological pH, which violates the strict spatial and electronic requirements of the enzyme's active site, rendering the nucleotide incapable of competitive inhibition.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Biomolecules - Class 12
Concept	Nucleoside vs Nucleotide
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free