The ‘catalytic triad’ in the active centre of proteases contains the following amino acids?
**Core Concept**
The catalytic triad in the active center of proteases is a crucial structural element responsible for the enzymatic activity of these proteins. It is a highly conserved motif found in various serine proteases, such as trypsin and chymotrypsin.
**Why the Correct Answer is Right**
The catalytic triad typically consists of three amino acids: histidine, aspartic acid, and serine. The histidine residue acts as a general base, abstracting a proton from the serine residue, which then attacks the peptide bond, facilitating its cleavage. The aspartic acid residue stabilizes the transition state of the reaction, enhancing the enzyme's catalytic efficiency. This precise arrangement of amino acids enables proteases to efficiently hydrolyze peptide bonds.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct amino acids that make up the catalytic triad. While it may be a plausible combination, it is not the accurate answer.
**Option B:** This option can be eliminated because it lacks the histidine residue, which is essential for the catalytic activity of proteases.
**Option C:** This option is incorrect because it includes a lysine residue, which is not typically part of the catalytic triad in serine proteases.
**Option D:** This option is incorrect because it includes a glutamic acid residue, which is not commonly found in the catalytic triad of serine proteases.
**Clinical Pearl / High-Yield Fact**
The catalytic triad is a fundamental concept in understanding the mechanism of action of proteases. It is essential to recognize the specific amino acids involved in this motif to appreciate the enzymatic activity of these proteins.
**Correct Answer: C. Histidine, aspartic acid, and serine.**