Final answer:
The enzyme responsible for catalyzing the transfer of the polypeptide in the P site to the amino acid in the A site during elongation is peptidyl transferase, an integral component of the 50S ribosomal subunit involved in the formation of peptide bonds in the protein synthesis process.
Step-by-step explanation:
During elongation, the enzyme that catalyzes the transfer of the polypeptide in the P site to the amino acid in the A site is peptidyl transferase. This RNA-based ribozyme is integrated into the 50S ribosomal subunit and plays a crucial role in protein synthesis. As the ribosome steps through the mRNA sequence, tRNA molecules sequentially occupy the A, P, and E sites. Charged tRNAs enter the A site bringing new amino acids that are then added to the growing polypeptide chain by the formation of peptide bonds. The energy for this process is derived from GTP hydrolysis, which is catalyzed by specific elongation factors.
Peptidyl transferase facilitates the formation of peptide bonds between the amino group of the amino acid attached to the A-site tRNA and the carboxyl group of the polypeptide bound to the P-site tRNA, thus elongating the polypeptide chain. The ribosome then translocates, moving the empty tRNA to the E site for expulsion, as the tRNA bearing the nascent polypeptide chain relocates from the A site to the P site, making room for a new aminoacyl-tRNA to enter the A site.