Which enzyme is inhibited by antiglycolytic agents?

• A. Hexokinase
• B. Pyruvate kinase
• C. Enolase
• D. Lactate dehydrogenase

Answer: (C)

Antiglycolytic agents work to stop glycolysis so that glucose isn’t broken down after the blood is drawn. The enzyme targeted by these agents is enolase. Fluoride, commonly used as the antiglycolytic component in glucose tubes, inhibits enolase by forming a complex with Mg2+ in the enzyme’s active site, preventing the conversion of 2-phosphoglycerate to phosphoenolpyruvate. Blocking this late step halts glycolysis and preserves glucose levels during handling. The other enzymes listed catalyze earlier or later steps and aren’t the usual targets of these inhibitors in routine practice.