19 - Lecture 14: Enzymatic Kinetics 2 Monday, August 23,...

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Unformatted text preview: Lecture 14: Enzymatic Kinetics 2 Monday, August 23, 2010 Many enzymes can be INHIBITED via the interaction of small molecules and ions. There are two principal ways that this can happen: COMPETITIVE and UNCOMPETITIVE inhibition. They are different in whether or not a substrate directly binds the active site or some other site in the protein. Monday, August 23, 2010 Many drugs and other therapeutics are molecules that are designed to inhibit specific enzymes in order to effect a disease process. An example of this is the chemotherapeutic METHOTREXATE, which acts against cells that are rapidly dividing by inhibiting the synthesis of dTTP. Dihydrofolate reductase converts dihydrofolate to tetrayhydrofolate, an essential cofactor in dTTP synthesis; methotrexate binds tightly to DH reductase, preventing it from making tetrahydrofolate. NOTE their chemical similarity! Monday, August 23, 2010 Monday, August 23, 2010 The above two forms of inhibition are referred to as REVERSIBLE inhibition in that the inhibitor can freely bind and dissociate, just like a substrate. On the other hand, we can also have IRREVERSIBLE inhibition, in which the inhibitor inactivates the enzyme, often by chemically modifying it Monday, August 23, 2010 Modification of a critical serine or cysteine residue destroys the catalytic active site of the enzyme, which cannot be undone Monday, August 23, 2010 Another good example of a irreversible inhibitor is PENICILLIN, which acts against enzymes responsible for synthesis of the bacterial cell wall The beta-lactam ring contains a highly reactive chemical bond, which is critical for the activity of the enzyme....
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19 - Lecture 14: Enzymatic Kinetics 2 Monday, August 23,...

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