Creatine kinase

• • Creatine is a molecule that is produced by the liver
• Creatine holds on to phosphate in skeletal and cardiac muscle
• • CK enzyme structure/components
  • MW - 82k daltons 
• CK enzyme is a dimer, made up of two monomers
• Three isoenzymes of creatine kinase:

  CK-MM, CK-BB, CK-MB
• CK-1 is CK-BB
• CK-3 is CK-MM
• CK-MM comprises 94-100% of normal serum CK
• skeletal: 99% or more of CK in skeletal muscle is CK-MM

  Cardiac: 80% of CK in cardiac muscle is CK-MM
• CK-2 is CK-MB
• CK-MB is a major indicator of MI
• CK-MB levels when an MI occurs rises in 4-8 hours, peak at 12-24 hours, normal 48-72 hours later 
• Ig complex is also called type 1 macro-CK
• oligomeric Ck-Mt is called type 2 Macro-CK
• Ig complex or type 1 - CK-BB or CK-MM complexed with immunoglobulins
• the preferred method for total Ck assays is the backward method
• optimal pH for forward method of Ck assay is 9.0
• the wavelength used for the forward Ck assay is UV light
• optimal pH for backward method is

  • Optimal pH is 6.8
  • much quicker reaction
• hemolysis interferes with CK measurement as the red cells have adenylate kinase, which converts ADP to ATP
• sunlight interferes with CK measurement as sunlight deactivates CK
• creatine kinase is found in brain, skeletal muscle, and cardiac muscle