Question

Adenosine Monophosphate and Guanosine Monophosphate are formed from

• A. Inosine Monophosphate
• B. Xanthine Monophosphate
• C. Glutamine
• D. Carbamoyl phosphate

Hint:

Think of IMP as the "fork in the road" for purine synthesis.
It branches off to become either AMP (via aspartate) or GMP (via oxidation to XMP).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Purine nucleotides (adenosine and guanosine) are synthesized through a multi-step de novo pathway that builds the purine ring on a ribose-5-phosphate scaffold.
This pathway leads to a common branch-point intermediate, which is then converted into either AMP or GMP.

Step 2: Detailed Explanation:
The de novo purine synthesis pathway begins with PRPP (phosphoribosyl pyrophosphate).
Through a series of enzymatic steps, the purine ring is assembled to form Inosine Monophosphate (IMP), which contains the base hypoxanthine.
IMP serves as the common precursor and branch point for both adenylate and guanylate pathways:
To synthesize AMP, IMP is condensed with aspartate to form adenylosuccinate (catalyzed by adenylosuccinate synthetase), which is then cleaved to release fumarate and AMP.
To synthesize GMP, IMP is oxidized to Xanthine Monophosphate (XMP) by IMP dehydrogenase. XMP is then aminated using glutamine to produce GMP.
Because both pathways originate from IMP, it is the key parent nucleotide for the synthesis of all purines.

Step 3: Final Answer:
Both Adenosine Monophosphate (AMP) and Guanosine Monophosphate (GMP) are synthesized from the branch-point precursor Inosine Monophosphate (IMP).