Question

The following enzyme of urea cycle is a crucial marker for hepatic disease

• A. Carbamoyl phosphate synthase
• B. Arginase
• C. Aspartate Transaminase
• D. Alanine Transaminase

Hint:

While AST and ALT are common liver panels, Arginase is a direct enzyme of the urea cycle and is almost entirely liver-specific.
This makes it a highly specific biomarker for hepatocyte damage.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The liver is the primary organ responsible for the detoxification of ammonia via the urea cycle.
Enzymes that participate exclusively in the urea cycle are highly concentrated within hepatocytes, making them potential markers for liver injury.

Step 2: Detailed Explanation:
Arginase (specifically Arginase-1) is the final enzyme of the urea cycle, catalyzing the hydrolytic cleavage of arginine to yield urea and ornithine.
Arginase-1 is almost exclusively expressed in the cytoplasm of hepatocytes.
Because of this high tissue specificity, any damage to the liver parenchyma (such as acute hepatitis or toxic liver injury) causes arginase to leak into the bloodstream.
While Aspartate Transaminase (AST) and Alanine Transaminase (ALT) are widely used clinical markers for liver disease, they are transaminases rather than core enzymes of the urea cycle itself.
Furthermore, AST is also found in high concentrations in cardiac and skeletal muscle, making it less specific to the liver than arginase.
Therefore, among the actual enzymes of the urea cycle, arginase serves as a highly specific clinical marker for hepatic disease.

Step 3: Final Answer:
The urea cycle enzyme that serves as a specific marker for hepatic disease is arginase.