Which lyase is clinically significant?

• A. Aldolase
• B. Citrate lyase
• C. Malate synthase
• D. Pyruvate lyase

Answer: (A)

Aldolase is the lyase with clinical significance because it plays a key role in glycolysis by breaking fructose-1,6-bisphosphate into two triose phosphates. In humans, serum aldolase can rise when muscle tissue is damaged or diseased, making it a useful, though nonspecific, clinical marker for muscle injury (and occasionally liver or other tissue damage). The other enzymes listed are not typically present in humans in a form that is measured clinically: malate synthase is part of a glyoxylate cycle found in microbes and plants, not human metabolism; citrate lyase and pyruvate lyase are not standard diagnostic enzymes in human clinics. Thus aldolase stands out as the clinically relevant lyase.