Which enzyme is more closely associated with muscle tissue than with liver tissue?

Which enzyme is more closely associated with muscle tissue than with liver tissue?

• A. Alanine aminotransferase
• B. Creatine kinase
• C. Alkaline phosphatase
• D. Gamma-glutamyltransferase

Answer: (B)

Creatine kinase is the enzyme most closely linked to muscle tissue because it sits in high abundance in skeletal and cardiac muscle and plays a key role in rapidly regenerating ATP during muscle contraction by transferring a phosphate from phosphocreatine to ADP. When muscle cells are damaged, CK leaks into the blood, making its serum levels a classic marker of muscle injury. The other enzymes are less specific to muscle: alanine aminotransferase is concentrated mainly in the liver (with some presence in muscle), alkaline phosphatase is abundant in bone and bile ducts, and gamma-glutamyltransferase is a liver/biliary marker. So the muscle-specific enzyme among these is creatine kinase.

Creatine kinase is the enzyme most closely linked to muscle tissue because it sits in high abundance in skeletal and cardiac muscle and plays a key role in rapidly regenerating ATP during muscle contraction by transferring a phosphate from phosphocreatine to ADP. When muscle cells are damaged, CK leaks into the blood, making its serum levels a classic marker of muscle injury. The other enzymes are less specific to muscle: alanine aminotransferase is concentrated mainly in the liver (with some presence in muscle), alkaline phosphatase is abundant in bone and bile ducts, and gamma-glutamyltransferase is a liver/biliary marker. So the muscle-specific enzyme among these is creatine kinase.