Which of the following enzymes are classified as serine proteases based on their catalytic mechanism?

Introduction:
Enzyme families are often grouped by their catalytic residues and mechanisms. Serine proteases utilize an activated serine (with His and Asp) to perform nucleophilic attack on peptide bonds. This question asks you to recognize classical members of this family.

Given Data / Assumptions:

• Serine proteases possess the catalytic triad Ser-His-Asp.
• They proceed via acyl-enzyme and deacylation steps.
• Trypsin, chymotrypsin, and elastase are textbook examples.

Concept / Approach:
Although their specificity pockets differ, trypsin, chymotrypsin, and elastase share the same core chemistry centered on Ser 195 activation through a charge-relay system. Therefore, all listed enzymes fall under the serine protease class.

Step-by-Step Solution:

Verification / Alternative check:
Active-site serine can be specifically inhibited by diisopropyl fluorophosphate (DFP) and related reagents across these enzymes, confirming a shared mechanism.

Why Other Options Are Wrong:

• Each single enzyme alone misses the completeness of the set.
• None of these: contradicts well-established classifications.

Common Pitfalls:
Assuming that different specificities imply different catalytic classes; here, specificity arises from the binding pocket, not the chemistry.

Final Answer:
All of these