Which acute-phase reactant inhibits enzymatic proteolysis and has the highest concentration among plasma protease inhibitors?

Which acute-phase reactant inhibits enzymatic proteolysis and has the highest concentration among plasma protease inhibitors?

• A. C-reactive protein
• B. Haptoglobin
• C. a2-Macroglobulin
• D. a1-Antitrypsin

Answer: (D)

The main idea here is identifying a major protease inhibitor that also acts as an acute‑phase reactant. Alpha-1 antitrypsin is a serine protease inhibitor produced by the liver that inhibits proteolytic enzymes such as neutrophil elastase, trypsin, and other proteases, protecting tissues from enzymatic damage during inflammation. It rises as part of the acute-phase response, increasing the amount of this protective inhibitor available when inflammation is present. Because of its abundance in plasma relative to other protease inhibitors, it is the primary reservoir of protease-inhibiting activity in the circulation. The other proteins listed don’t fit this combination: C-reactive protein is a key acute-phase protein involved in opsonization and complement activation rather than protease inhibition; haptoglobin binds free hemoglobin to prevent oxidative damage; alpha-2-macroglobulin is a broad-spectrum protease inhibitor but is present at lower levels and its role, while important, does not outpace alpha-1 antitrypsin in terms of concentration.

The main idea here is identifying a major protease inhibitor that also acts as an acute‑phase reactant. Alpha-1 antitrypsin is a serine protease inhibitor produced by the liver that inhibits proteolytic enzymes such as neutrophil elastase, trypsin, and other proteases, protecting tissues from enzymatic damage during inflammation. It rises as part of the acute-phase response, increasing the amount of this protective inhibitor available when inflammation is present. Because of its abundance in plasma relative to other protease inhibitors, it is the primary reservoir of protease-inhibiting activity in the circulation. The other proteins listed don’t fit this combination: C-reactive protein is a key acute-phase protein involved in opsonization and complement activation rather than protease inhibition; haptoglobin binds free hemoglobin to prevent oxidative damage; alpha-2-macroglobulin is a broad-spectrum protease inhibitor but is present at lower levels and its role, while important, does not outpace alpha-1 antitrypsin in terms of concentration.