Q.31 Which of the enzyme catalyses the formation of peptide bond between two amino acids?
(1) Peptidases
(2) Peptidyltransferase
(3) Phosphodiesterase
(4) Proteases
Which Enzyme Catalyzes Peptide Bond Formation: Peptidyltransferase Explained
Peptidyltransferase is the key enzyme responsible for forming peptide bonds between amino acids during protein synthesis. This SEO-optimized article breaks down the MCQ options for biology students and researchers.
Correct Answer
The correct answer is (2) Peptidyltransferase. This ribozyme, located in the large ribosomal subunit, catalyzes the nucleophilic attack forming a peptide bond between the carboxyl group of one amino acid (on P-site tRNA) and the amino group of another (on A-site tRNA) during translation elongation.
Role in Protein Synthesis
Peptidyltransferase facilitates polypeptide chain growth by linking amino acids, releasing water in a condensation reaction. It is RNA-based (23S rRNA in prokaryotes), highlighting the ribosome’s ribozyme activity. This step occurs after codon recognition by aminoacyl-tRNA.
Option Analysis
| Option | Description | Correct for Peptide Bond? |
|---|---|---|
| (1) Peptidases | Hydrolase enzymes that cleave peptide bonds in proteins/peptides, aiding digestion or regulation (e.g., trypsin). They break, not form, bonds | No |
| (2) Peptidyltransferase | Ribosomal ribozyme forming peptide bonds between nascent chain and new amino acid in translation . | Yes |
| (3) Phosphodiesterase | Hydrolyzes phosphodiester bonds in nucleic acids (DNA/RNA) or cyclic nucleotides (e.g., cAMP). No role in amino acid linkages | No |
| (4) Proteases | Endopeptidases/exopeptidases degrading proteins by hydrolyzing peptide bonds (e.g., pepsin, chymotrypsin). Opposite of synthesis | No |
Why Peptidyltransferase Stands Out
Unlike protein-degrading enzymes (peptidases, proteases), peptidyltransferase uniquely drives anabolism in ribosomes. Its discovery as a ribozyme revolutionized views on RNA’s catalytic role, per the “RNA world” hypothesis. Essential for molecular biology, genetics exams.
