An inactive protein precursor of a digestive enzyme is secreted into the pancreatic duct. It must undergo limited proteolytic cleavage to become catalytically active. Such an inactive precursor enzyme is best termed:

• A Zymogen ✓
• B Apoenzyme
• C Holoenzyme
• D Prosthetic enzyme

Explanation

B zymogen (proenzyme) is an inactive precursor activated by cleavage of specific peptide bonds, e.g., trypsinogen, pepsinogen, proelastase. An apoenzyme is the protein portion of an enzyme lacking its required cofactor; the catalytically complete apoenzyme-plus-cofactor complex is the holoenzyme. B prosthetic group is a tightly bound cofactor such as heme or biotin. Zymogen activation is irreversible and amplifies signals such as the clotting and complement cascades.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.