Aspartate (Asp) is an amino acid with the structure NH₂-CH(CH₂-COOH)-COOH. Given below are biosynthetic processes occurring in cells:

A. Protein synthesis

B. De novo synthesis of inosine monophosphate and orotic acid

C. Synthesis of adenosine monophosphate from inosine monophosphate

D. Glutathione synthesis

Which one of the following options correctly represents all the biosynthetic process(es) wherein Asp is involved as a precursor?

Correct option is D

Aspartate (Asp) plays a significant role in multiple biosynthetic pathways. Let's analyze each option:

A. Protein synthesis

• Aspartate is one of the 20 standard amino acids used in protein synthesis. Asp is involved.

B. de novo synthesis of inosine monophosphate (IMP) and orotic acid

• Aspartate participates in the purine synthesis pathway, contributing to IMP (precursor of AMP and GMP).
• Aspartate is also involved in pyrimidine biosynthesis, forming orotic acid, a precursor to UMP (uridine monophosphate). Asp is involved.

C. Synthesis of adenosine monophosphate (AMP) from inosine monophosphate (IMP)

• In the conversion of IMP to AMP, Aspartate donates a nitrogen group in the reaction catalyzed by adenylosuccinate synthetase. Asp is involved.

D. Glutathione synthesis

• Glutathione (GSH) is synthesized from glutamate, cysteine, and glycine.
• Aspartate is not involved in this process. Asp is NOT involved.

Correct Answer:

(4) A, B, and C

Information Booster:

1. Aspartate as a Nitrogen Donor: It donates nitrogen groups in nucleotide biosynthesis.
2. Aspartate in the Urea Cycle: It helps in eliminating excess nitrogen via urea formation.
3. Role in TCA Cycle: Aspartate is an intermediate in the malate-aspartate shuttle.
4. Aspartate in Pyrimidine Synthesis: It is a key component of pyrimidine rings.
5. Aspartate in Neurotransmission: It acts as an excitatory neurotransmitter in the brain.
6. Essential for DNA and RNA Synthesis: Without Asp, nucleotides (purines and pyrimidines) cannot be formed.
7. Used in Amino Acid Biosynthesis: It is a precursor for asparagine.