ENZYME INHIBITION AND REGULATION Flashcards
a non-prescription drug irreversibly inhibits prostaglandins and thromboxane synthesis by inhibiting cyclooxygenase
ASPIRIN
the inactive precursor of a proteolytic enzyme
zymogen or proenzyme
Any substance that can diminish the velocity of an enzyme-catalyzed reaction
inhibitor
regulated by molecules called effectors (also called modifiers) that bind noncovalently at a site other than the active site
Allosteric enzymes
inhibitors bind to enzymes through covalent bonds
irreversible inhibitors
Effectors that inhibit enzyme activity
negative effectors
inhibitors typically bind to enzymes through noncovalent bonds, thus dilution of the enzyme–inhibitor complex results in dissociation of the reversibly bound inhibitor
Reversible inhibitors
those that increase enzyme activity
positive effectors
two most commonly encountered types of reversible inhibition
competitive
noncompetitive
catalyzed by a family of enzymes called protein kinases that use adenosine triphosphate (ATP) as a phosphate donor
Phosphorylation
This type of inhibition occurs when the inhibitor binds reversibly to the same site that the substrate would normally occupy and, therefore, competes with the substrate for that site
Competitive inhibition
Phosphorylation reactions are catalyzed by a family of enzymes called
protein kinases
an example of competitive inhibitor
STATIN DRUGS
TRUE / FALSE:
Enzymes subject to regulation of synthesis are often those that are needed at only one stage of development or under selected physiologic conditions
TRUE
structural analogs of the natural substrate for this enzyme, and compete effectively to inhibit HMG-CoA reductase
STATIN DRUGS
regulating cellular enzyme activity based on the production of enzymes in an inactive form
Proteolytic enzyme and zymogen
This type of inhibition is recognized by its characteristic effect on Vmax
Noncompetitive inhibition
generated in an inactive form and then later, when they are needed, are converted to their active form
proteolytic enzymes
occurs when the inhibitor and substrate bind at different sites on the enzyme
Noncompetitive inhibition
an enzyme that catalyzes the breaking of peptide bonds that maintain the primary structure of a protein
proteolytic enzyme
a molecule that inactivates enzymes by forming a strong covalent bond to an amino acid side-chain group at the enzyme’s active site
irreversible enzyme inhibitor
