Enzymes: Isozymes and Regulation

  1. what are isozymes
    enzymes that have multiple forms, is different in structure, but catalyze the same reactions
  2. what are nonfunctional plasma enzymes
    • enzymes with no physiologic function even with substrate present.
    • Presence of these enzymes may reflect destruction of cells, from which they originate
  3. clinical use of acid pohsphatase
    carcinoma of prostate
  4. clinical use of alanine aminotransferase (ALT)
  5. clinical use of alkaline phosphatase
    bone disorders; obstructuive liver disease
  6. clinical use of amylase
    acute pancreatitis
  7. clinical use of ceruloplasmin
    wilson's disease
  8. clinical use of  glutamyl transpeptidase
    liver disease
  9. what are the isozymes that indicate myocardial infarction
    • creatinine phosphokinase (CPK): MB isozyme appears w'in 24 hrs, normal in 48 hrs
    • lactate dehydrogenase (LDH): H4 isozyme present for 2 wks
    • Asparatate amino Transferase (AST): peaks at 2 days, normal by 4 days
    • cardiac troponins (T and I): appears first w/in 4-6 hrs, may be high for up to 2 weeks
  10. clinical use of lipase
    acute pancreatitis
  11. what are the dimer subunits of creatinine phosphokinase (CPK)
    • MM isozyme - muscle
    • BB isozyme - brain
    • MB isozyme - heart
  12. what are the simer subunits of lactate dehydrogenase (LDH)
    • H4 isozyme - heart (aerobic)
    • M4 isozyme - muscle (anaerobic)
  13. what is the clinical significance of troponin
    T and I are cardiac regulatory proteins that control the calcium mediated interaction between actin and myosin
  14. what is the clinical correlate for amylase
    breaks down starch to glucose
  15. what are the 5 forms of enzyme regulation
    • substrate availability
    • allosteric regulation
    • post translational modification
    • interaction of control proteins
    • zymogens
  16. describe substrate availability in terms of enzyme regulation
    activity determined by concentration of substrate. not enough substrate won't allow enzyme to activate
  17. describe allosteric regulation in terms of enzyme regulation
    when non competitive inhibitor binds to the allosteric site this inhibits the binding of substrate at active site
  18. describe relaxed state enzyme and tense state enzyme
    • relaxed state - active enzyme (high affinity for substrate)
    • tense state - inactive enzyme (low affinity for substrate
  19. describe post translational modification in terms of enzyme regulation
    • a modification in a protein by the covalent attachment of a chemical group to the amino acid
    • ex. phosphorylation, acylation, hydroxylation
  20. describe interactions with control proteins in terms of enzyme regulation
    • attachment of inhibitory subunit (protein) that deactivates the enzyme
    • ex. cyclic AMP
  21. describe zymogens in terms of enzyme regulation
    • zymogens: an inactive substance that is converted into an enzyme when activated by another enzyme.
    • The enzymes are activated by the removal of a portion of the peptide chain (proteolysis)
Card Set
Enzymes: Isozymes and Regulation
regulation, allosteric regulation, post translational modification