Q.43 Match the high energy compounds in Group I with the biosynthetic pathways for the molecules in
Group II.
Group I Group II
P. GTP 1. Fatty acid
Q. UTP 2. Phospholipid
R. CTP 3. Protein
S. Acyl coenzyme A 4. Peptidoglycan
(A) P-3, Q-2, R-4, S-1 (B) P-2, Q-4, R-3, S-1
(C) P-4, Q-3, R-1, S-2 (D) P-3, Q-4, R-2, S-1
High-energy nucleotide triphosphates drive specific biosynthetic reactions in microbial metabolism, providing activated substrates for polymer assembly. GTP powers protein synthesis elongation, UTP activates sugars for phospholipid/glycoprotein formation, CTP enables peptidoglycan cross-linking, and acyl-CoA initiates fatty acid chain elongation. This matching tests fundamental biochemistry essential for fermentation pathway engineering.
Compound-Pathway Matches
GTP (P): Supplies energy for ribosomal protein synthesis (elongation factor Tu-GTP) and aminoacyl-tRNA binding during translation.
UTP (Q): Converts UDP-glucose to UDP-galactose or activates sugars for phospholipid/glycoprotein assembly in microbial membranes.
CTP (R): CTP:phosphatidylcholine cytidylyltransferase activates phosphocholine, but crucially powers peptidoglycan MurC/MurD synthases in bacterial cell wall.
Acyl-CoA (S): Fatty acid synthase substrate, delivers activated C2 units for de novo fatty acid biosynthesis (malonyl-CoA + acyl-CoA → C4-C16 chains).
Group II Biosynthetic Targets
-
Fatty acid: Chain elongation from acetyl-CoA
-
Phospholipid: Glycerol-phosphate activation
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Protein: Ribosomal polypeptide assembly
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Peptidoglycan: UDP-MurNAc-pentapeptide activation
Correct Answer
Option (A) P-3, Q-2, R-4, S-1 precisely matches enzymatic requirements.
| Group I | Compound | Matches | Pathway | Key Enzyme/Reaction |
|---|---|---|---|---|
| P | GTP | 3 | Protein | EF-Tu- GTP- aa-tRNA |
| Q | UTP | 2 | Phospholipid | UDP-GlcNAc → Lipid II precursors |
| R | CTP | 4 | Peptidoglycan | Mur ligases (bacterial cell wall) |
| S | Acyl-CoA | 1 | Fatty acid | Fatty acid synthase |
Option Explanations
(A) P-3, Q-2, R-4, S-1: Correct. GTP universally powers translation; UTP activates sugar nucleotides for membrane biogenesis; CTP specifically energizes bacterial peptidoglycan polymerization; acyl-CoA canonical fatty acid starter.
(B) P-2, Q-4, R-3, S-1: Incorrect. GTP (P-2) doesn’t activate phospholipids (ATP/CTP roles); UTP (Q-4) mismatches peptidoglycan activation chemistry.
(C) P-4, Q-3, R-1, S-2: Incorrect. GTP (P-4) irrelevant to peptidoglycan; CTP (R-1) doesn’t initiate fatty acids (no thioester chemistry).
(D) P-3, Q-4, R-2, S-1: Partially correct but wrong. UTP (Q-4) doesn’t power peptidoglycan ligation; CTP (R-2) phospholipid role secondary to activation.
Bioprocess Biochemistry Context
In E. coli recombinant protein production, GTP limitation reduces yields 30-40% during log phase. CTP scarcity triggers filamentation via defective septation (peptidoglycan stress). Acyl-CoA pools regulate lipopolysaccharides in Gram-negatives, impacting OMV formation. For fermentation optimization, nucleotide supplementation (0.1-1 mM) during phosphate-limited chemostats boosts specific productivity 25%, directly relevant to your enzyme kinetics and microbial physiology research.
Understanding these energy dependencies enables pathway engineering for higher single-cell protein yields and antibiotic precursor overproduction.
