Which of the following is an enzyme commonly measured in clinical chemistry?

• A. CK
• B. Calcium
• C. Magnesium
• D. Phosphate

Answer: (A)

Enzymes measured in clinical chemistry are indicators of tissue injury, since they are released into the blood when cells are damaged. Creatine kinase is an enzyme that sits mostly in muscle tissues, including skeletal and cardiac muscle. When muscle damage occurs—such as from a heart attack, severe exercise, or muscle injury—CK leaks into the bloodstream, and its level rises in a measurable way. Clinically, CK levels (often with its CK-MB isoform for cardiac involvement) help assess the extent of muscle or heart muscle injury.

Calcium, magnesium, and phosphate, on the other hand, are minerals or electrolytes. They are important for various physiological processes and are measured for different reasons, but they are not enzymes. So they don’t serve as enzyme markers like creatine kinase does.

Thus, creatine kinase is the enzyme commonly measured in clinical chemistry.