Liver and Enzyme Function Quiz

Liver Enzymes

• Aspartate Transaminase (AST) / Serum Glutamate Oxaloacetate Transaminase (SGOT):

  • Catalyzes the reaction of L-Aspartate + α-ketoglutarate → Oxaloacetate + L-Glutamate
  • Found in high concentrations in heart, skeletal muscle, liver, kidneys, and red blood cells.
  • Elevated levels indicate damage to these tissues (e.g., heart attack, hepatitis, trauma).

• Alanine Transaminase (ALT) / Serum Glutamic Pyruvic Transaminase (SGPT):

  • Catalyzes the reaction of L-Alanine + α-ketoglutarate → Pyruvate + L-Glutamate
  • Primarily found in liver, skeletal muscle, kidneys, and heart.
  • Elevated levels suggest liver disease (hepatitis, cirrhosis), circulatory problems (shock), or trauma/surgery.
  • ALT elevation often precedes bilirubin elevation during viral hepatitis.

Other Enzymes

• Lactate Dehydrogenase (LDH):

  • Catalyzes the reversible reaction of lactate and pyruvate using NAD+/NADH.
  • Easily measured.
  • Present in many tissues (heart, skeletal muscle, liver, kidneys, brain, red blood cells).
  • High levels are common in many conditions, not a very specific diagnostic marker (e.g., hemolysis, heart attack). Increased LDH levels are associated with conditions such as anemia, acute leukemia and lymphoma, heart attack, rejection of kidney transplants, and viral hepatitis.

• Creatine Kinase (CK) / Phosphokinase:

  • Abundant in heart muscle, skeletal muscle, brain, and smooth muscle.
  • Increased levels often seen in heart attack, muscle damage, or during the neonatal period.

• CK Isoenzyme:

  • Composed of M (muscle) and B (brain) subunits.
  • CK-MM predominant in skeletal and cardiac muscle.
  • CK-MB is about 35% of cardiac CK activity; increased levels suggest cardiac muscle damage.
  • CK-MB may also increase in other tissues like pancreatic juice, saliva, gonads, fallopian tubes and be excreted in urine.

Pancreatic Enzymes

• Pancreatitis:
  • Increased levels of digestive enzymes like amylase, lipase, and trypsin are detected in the blood due to pancreatitis. This happens due to damage to the pancreas and its duct. Amylase typically enters the bloodstream and is excreted in the urine.

Other Diagnostic Enzymes

• Alkaline Phosphatase (ALP):

  • Catalyzes the hydrolysis of organic phosphates at alkaline pH.
  • Found in many tissues, especially important for bone development.
  • Elevated levels can indicate bone disorders, or blockages of bile ducts (cholestasis) in liver.

• Acid Phosphatase (ACP):

  • Present in prostate cells, liver, red blood cells, platelets and bones.
  • Measurement of prostate-specific antigen (PSA) used in prostate carcinoma diagnosis. ACP in the plasma is a result of its release through the prostate ducts into the urethra.

• γ-glutamyl transferase (GGT):

  • Abundant in liver cells, kidneys, pancreas, and prostate.
  • Plasma GGT activity is generally higher in men.
  • Elevated GGT can indicate liver disease or excessive alcohol use. Drug/alcohol exposure can boost GGT production without cell damage.
  • Elevated GGT levels are a useful indicator of both alcohol-induced liver disease and liver cirrhosis.

Test your knowledge on liver enzymes such as AST, ALT, and LDH. This quiz covers their functions, significance in tissue damage, and implications of elevated levels. Perfect for biology or medical students looking to enhance their understanding of enzyme roles in health and disease.