In skeletal muscle, which marker is most abundant according to the given abundance order CK1 > AST > Aldolase > LD4,5?

• A. CK1
• B. AST
• C. Aldolase
• D. LD4,5

Answer: (A)

Muscle tissue relies heavily on the phosphocreatine system to quickly regenerate ATP during contraction, so the muscle-specific creatine kinase isoenzyme is present in very high amounts. This CK isoenzyme, represented here as CK1, is the most abundant marker in skeletal muscle because it directly supports rapid energy buffering, making it the dominant enzyme in this tissue.

Following that, AST is present in substantial quantities in muscle as part of amino transfer reactions, but it is also abundant in other tissues like liver and heart, so it’s the next most plentiful marker among these muscle-related enzymes.

Aldolase A, while a key glycolytic enzyme in muscle, does not reach the same overall concentration as CK-MM or AST, so it comes next in abundance.

LD4,5 refers to LDH isoforms that are less represented in skeletal muscle compared with CK-MM, AST, and aldolase, making them the least abundant of the group.