20. Proteolytic enzymes are usually biosynthesized as large, inactive precursors known as
(A) holoenzymes
(B) ribozyme
(C) zymogens
(D) apoenzymes
Proteolytic enzymes are biosynthesized as large, inactive precursors called zymogens to prevent self-digestion of producing cells. The correct answer is (C) zymogens.
Correct Answer
Zymogens serve as inactive precursors for proteolytic enzymes, such as trypsinogen or pepsinogen, which are activated by cleavage only at specific sites like the digestive tract. This mechanism protects cells from damage by potent proteases during synthesis and storage. Examples include pancreatic enzymes stored in zymogen granules until hormonal signals trigger release and activation.
Option Breakdown
| Option | Definition & Role | Why Incorrect for Proteolytic Precursors |
|---|---|---|
| (A) Holoenzymes | Complete, active enzyme complexes with cofactor bound to apoenzyme . | Represents active form, not inactive precursor . |
| (B) Ribozyme | RNA molecule with catalytic activity, like self-splicing introns . | Non-protein enzyme; unrelated to protein precursors . |
| (C) Zymogens | Inactive proenzymes activated by proteolysis; standard for proteases . | Correct – Matches query exactly . |
| (D) Apoenzymes | Protein portion of enzyme lacking cofactor; inactive until binding . | Lacks cofactor, not larger precursor form . |
1 Comment
Sonal Nagar
January 15, 2026zymogens