Multiple Choice
The following polypeptide N-G-I-F-D-A-Y-G-N-T-W-R-A-P-C-F-V-A is cleaved by chymotrypsin to produce multiple peptide fragments. Based on the specificity of chymotrypsin cleavage, how many peptide fragments are produced?
8. Protein Function
Chymotrypsin
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Which amino acids in chymotrypsin's active site are critical participants in the cleavage of the substrate?
A
His, Ser, Asn.
B
His, Ser, Asp.
C
His, Ser.
D
Asp, Lys.
Verified step by step guidance1
Understand the role of chymotrypsin: Chymotrypsin is a serine protease enzyme that cleaves peptide bonds in proteins. Its active site contains amino acids that are crucial for its catalytic activity.
Identify the catalytic triad: The active site of chymotrypsin contains a catalytic triad composed of three amino acids: Histidine (His), Serine (Ser), and Aspartic acid (Asp). These amino acids work together to facilitate the cleavage of peptide bonds.
Examine the function of each amino acid: Serine acts as the nucleophile that attacks the peptide bond, Histidine serves as a base to deprotonate Serine, and Aspartic acid stabilizes the positive charge on Histidine, enhancing its ability to act as a base.
Consider the incorrect options: Asn (Asparagine) and Lys (Lysine) are not part of the catalytic triad in chymotrypsin. Asparagine does not participate in the catalytic mechanism, and Lysine is not involved in the active site of chymotrypsin.
Conclude with the correct participants: The critical amino acids in chymotrypsin's active site for substrate cleavage are Histidine (His), Serine (Ser), and Aspartic acid (Asp). These form the catalytic triad essential for its enzymatic function.
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