Mitochondrial Aspartate Aminotransferase

Mitochondrial Aspartate Aminotransferase (mAST) is one of the two isoenzymes of AST:

• Cytosolic AST (cAST)
• Mitochondrial AST (mAST)

mAST is located inside the mitochondria of hepatocytes, especially in the centrilobular region.

1️⃣ Marker of Severe Hepatocellular Damage (Very Important)

mAST is released into the blood only when there is:

• Severe liver cell necrosis
• Mitochondrial damage
• Extensive hepatocyte destruction

Markedly Elevated In:

• Acute severe hepatitis
• Toxic liver injury
• Ischemic hepatitis
• Acute liver failure

👉 Indicates more severe liver injury compared to mild cytoplasmic damage.

2️⃣ Alcoholic Liver Disease

Alcohol causes:

• Mitochondrial damage
• Increased release of mAST

This explains why:

• AST > ALT
• AST/ALT ratio > 2 in alcoholic liver disease

Because AST includes a mitochondrial fraction.

3️⃣ Prognostic Significance

High mAST levels suggest:

• Extensive hepatocyte necrosis
• Poor prognosis in acute liver failure

4️⃣ Differentiation from Muscle Injury

• Total AST increases in muscle disease
• mAST is more liver-specific

Hence, mAST helps confirm hepatic origin of elevated AST.

5️⃣ Not Significantly Elevated In:

• Mild liver injury
• Bone disease
• Isolated muscle injury (minimal rise)