lesson 5

• Extracellular enzymes


  Enzymes that are synthesized in the cell but secreted from the cell to work internally
• Intracellular enzymes


  Enzymes that are synthesized and retained in the cell for the use of the cell itself
• If the enzymes are found in abundant amount in the blood, it could indicate damage to cells causing their leakage to the blood
• Determining organ damage through enzyme levels is a fairly invasive way and can be repeated
• Amylase


  Smallest enzyme, rises early in the case of acute pancreatitis, high sensitive but less specific, main sources are pancreas and salivary glands
• Lipase


  More specific to acute pancreatitis, LPS concentration is found primarily in the pancreas but there is also low levels in stomach and intestine
• High amylase but normal LPS = salivary gland involvement, High amylase and LPS = acute pancreatitis
• Acid phosphatase (ACP)


  Releases phosphate with the addition of water, works best at acidic pH, tissue sources include bones, liver, platelets, and prostate
• ACP is elevated in benign prostatic hyperplasia, prostatic carcinoma and hemolysis, and is also used in the investigation of rape since it is found in high amounts in the semen
• Alkaline phosphatase (ALP)


  Releases phosphate with the addition of water, works best at alkaline pH, rich in epithelial cells of the bile duct, can also be seen in intestine, placenta, and bone
• Children, pregnant women, and those eating fatty meals have higher ALP levels
• ALP increases in biliary tract obstruction and liver disorders, and is also elevated in bone disorders, healing bone repairs, and hyperparathyroidism
• Gamma glutamyl transferase (GGT)


  A transferase enzyme that transfers gamma-glutamyl group from a peptide, normally found in the kidney, brain, prostate, and bile duct
• GGT is more specific to bile duct obstruction than ALP, and can also be elevated in chronic alcoholism
• Within the hepatocyte, GGT exists in the smooth ER and is subjected to induction by warfarin, phenobarbital, phenytoin, and alcohol

  
• GGT levels can be 2-3x higher than the upper limit in chronic alcoholism, and go back to normal within 2-3 weeks if the patient stops drinking
• GGT is useful in differentiating high ALP from bile duct obstruction or from bone disorders
• Creatine kinase (CK)


  Associated with storage and regeneration of ATP, intracellular enzyme present in greatest amounts in skeletal muscle, myocardium, and brain

  
• CK peaks 3-6 hrs after the onset of a heart attack, peaks at 12-24 hours and returns normal within 48-72 hours
• CK levels are higher in men, and rise in the blood after exercise or any physical strenuous activities
• Elevated CK levels are associated with CNS disorders such as stroke, nerve degeneration, seizures, and shock, and can only be detected in the CSF due to damage in the BBB
• Aspartate aminotransferase (AST)


  Also known as serum glutamic oxaloacetic transaminase (SGOT), transferase enzyme, starts raising 6 to 8 hours after the symptom onset, reaches the peak level at 24 to 36 hours, returns back to normal after 5 days
• AST can also be found in skeletal muscles and liver, but is more abundant in the heart, so it is not very reliable in diagnosis
• Lactate dehydrogenase (LDH)


  Uses NAD/NADH as coenzyme, allows the transfer of hydrogen from lactate to NAD+, has many tissue sources - heart, RBC, skeletal muscles

  
• LDH is the least specific compared to other enzymes, starts to increase 12 hrs after the onset of heart attack
• Alanine aminotransferase (ALT)


  Also known as serum glutamic pyruvic transaminase (SGPT), can be found in the liver, more specific liver-specific than AST, higher elevations in liver disorder than in biliary obstruction (GGT)