Ch 10 Final Review: ID

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  1. Aspartate transcarbamoylase
    Catalyzes the condensation of aspartate and carbamoyl phosphate to form N-carbamoylaspartate and orthophosphate; functions in the committed step; inhibited by CTP; has a sigmoidal curve
  2. PALA
    Potent competitive inhibitor of ATCase, binding to the active site and blocking them; binds at sites between pairs of c chains; when it binds, the two catalytic trimers move farther and rotate about their axis of symmetry; the regulatory dimers rotate 15 degrees as well
  3. Homotropic effects
    The effects of substrates on allosteric enzymes; substrates generate the sigmoidal curve
  4. Heterotropic effects
    The effects of nonsubstrate molecules on allosteric enzymes; regulators shift the Km
  5. isozymes
    Enzymes that differ in amino acid sequence yet catalyze the same reaction; usually, the enzymes display different kinetic parameters, such as Km, or respond to different regulatory molecules; they are encoded by different genes; it permits the fine-tuning of metabolism to meet the needs of a given tissue or developmental stage
  6. Dedicated protein kinases
    Phosphorylate a single protein or several closely related ones
  7. Multifunctional protein kinases
    Modify many different targets: they have a wide reach and can coordinate diverse processes; ex: consensus sequence
  8. Consensus sequence
    Recognized by protein kinase A; is Arg-Arg-X-Ser or Thr-Z, where X is the small residue and Z is a large hydrophobic one; not required. For ex, lysine can substitute for an arg, causing less affinity
  9. Protein phosphatases
    Reverse the effects of kinases by catalyzing the removal of phosphoryl groups attached to proteins; the enzyme hydrolyzes the bond attaching the phosphoryl group; turn off signaling pathways that are activated by kinases
  10. cAMP
    An intracellular messenger formed by the cyclization of TP; activates protein kinase A, which alters activities of target proteins by phosphorylating specific serine and threonine residues
  11. zymogen (proenzyme)
    Inactive precursor of an protein (enzyme) that must be cleaved in order to activate it; the cleavage is irreversible
  12. common activator
    Trypsin is called the common activator because it acts on all the pancreatic zymogens
  13. master activation step
    the activation of trypsin by enteropeptidase
  14. enzymatic cascades
    Often employed in biochemical systems to achieve a rapid response; an initial signal institutes a series of steps, each step at which the signal is amplified
  15. fibrinopeptides
    The A and B peptides released upon thrombin cleavage of fibrinogen; if a fibrinogen is devoid of the fibrinopeptides, it is a fibrin monomer
  16. Pancreatic trypsin inhibitor
    a.       inhibits trypsin by binding very tightly to its active site it is a very effective substrate analog. It lies in the active site, positioned so that the side chain of lysine of the inhibitor interacts with the aspartate side chain in the specificity pocket of trypsin. Furthermore, the carbonyl group fits into the active site. Though the enzyme’s structure is unchanged, the inhibitor is preorganized into a complementary structure
  17. Alpha1-Antitrysin
    protects tissues form digestion by elastase; blocks elastase much more effectively than it blocks trypsin; it blocks the action of target enzymes by binding to their active sites
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Ch 10 Final Review: ID
Test Three
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