Which statement best explains why ALT is considered more liver-specific than AST?

• A. ALT is not liver-specific
• B. ALT is more liver-specific because it is more abundant in the liver and less present in muscle or other tissues
• C. AST is more liver-specific
• D. ALT is produced only during acute hepatic failure

Answer: (B)

The main idea is that how specific an enzyme is for a particular organ depends on where that enzyme is located in the body. Alanine aminotransferase (ALT) is highly concentrated in liver cells and present only in small amounts in muscle and other tissues. Aspartate aminotransferase (AST), on the other hand, is found not only in the liver but also in heart, skeletal muscle, kidney, brain, and other tissues, and even in mitochondria. Because ALT is more abundant in the liver and less present elsewhere, its release into blood during hepatocellular injury is more specific to the liver. AST can rise from damage to multiple tissues, making it less liver-specific. The statement captures this distribution-based rationale.