Which substance is NOT considered a liver enzyme?

Lactate dehydrogenase (LDH) is not classified as a liver enzyme, although it can be found in various tissues throughout the body, including the liver. LDH is an enzyme involved in the conversion of lactate to pyruvate and is a key player in metabolic processes, particularly in anaerobic respiration. Because it is present in many tissues, including muscle, heart, kidney, and the brain, LDH is often used as a marker for tissue damage or disease rather than for liver-specific function or damage.

In contrast, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) are enzymes that are significantly associated with liver function and disease. ALT is primarily found in the liver and is a sensitive indicator of liver cell injury. AST is also found in the liver, but it is present in other tissues as well, though it is often used in conjunction with ALT to assess liver health. Alkaline phosphatase is mainly associated with the bile ducts and liver, and its levels can indicate cholestasis or other liver conditions.

Therefore, lactate dehydrogenase is the correct answer as it is not exclusive to liver function, highlighting