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| A numerically small (low) Km reflects a ? ? of the enzyme for substrate. The rate of reaction is said to be ? order with respect to substrate. |
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| A numerically large (high) Km reflects a ? ? of enzyme for substrate because a high concentration of substrate is needed to half-saturate the enzyme. |
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| The rate of the reaction is directly proportional to the ? ? at all substrate concentrations |
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| If the enzyme concentration is ?, the initial rate of the reaction (Vi), as well as that of Vmax, are reduced to one half that of the original. |
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| When [S] is much less than Km, the velocity of the reaction is approximately proportional to the ? concentration. |
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When [S] is much greater than Km, the velocity is ? and equal to Vmax.
The rate of reaction is then independent of ? concentration, and is said to be ? order with respect to substrate concentration |
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| Km does not vary with the concentration of ? |
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| Km is numerically equal to the substrate concentration at which the reaction velocity is equal to 1/2? |
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| The effect of a competitive inhibitor is reversed by increasing ? At a sufficiently high ? concentration the reaction velocity reaches the Vmax observed in the absence of the inhibitor |
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| A competitive inhibitor increases the ? ? for a given substrate. |
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| On a Lineweaver-Burke plot the Vmax is unchanged but the inhibited and uninhibited reactions show different ? ? intercepts, indicating that the apparent Km is increased in the presence of the competitive inhibitor |
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| Noncompetitive inhibition can bind either free enzyme or the ? ?, thereby preventing the reaction from occurring. |
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| Noncompetitive inhibition can't be overcome by increasing the conc. of substrate. Thus, noncompetitive inhibitors decrease the ? of the reaction. |
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| Noncompetitive inhibitors don't interfere with the binding of substrate to enzyme. Thus, the enzyme shows the ? ? in the presence or absence of the noncompetitive inhibitor |
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| Noncompetitive inhibition is readily differentiated from competitive inhibition by plotting 1/Vo versus 1/[S] and noting that ? decreases in the presence of a noncompetitive inhibitor, whereas ? is unchanged |
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| Statin drugs like atorvastatin (Lipitor) and simvastatin (Zocor) are examples of ? ? |
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| Ex. of noncompetitive inhibitors: some inhibitors act by forming ? ? with specific groups of enzymes |
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| An example of a noncompetitive inhibitor is ? forming covalent bonds with sulfhydryl side chains of cysteine in proteins |
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