Biochemistry - Enzymes Study Guide


6.7 The Double Reciprocal or Lineweaver-Burk Plot

  • The Michaelis-Menten curve can be converted into a linear form by plotting 1/V01/V_0 versus 1/[S]1/[S], creating the Lineweaver-Burk Plot.

  • In this linear plot:

    • Values of Km and Vmax can be obtained from the intersections of its axes:

    • Slope = racK<em>mV</em>maxrac{K<em>m}{V</em>{max}}

    • y-intercept = rac1Vmaxrac{1}{V_{max}}

    • x-intercept = −rac1Km- rac{1}{K_m}

  • The equation can be expressed as:

6.8 Method to Determine Km and Vmax Accurately

  • The Lineweaver-Burk Equation allows for more precise determination:

6.9 Reversible Inhibition

  • Reversible inhibition is characterized by an inhibitor that can bind to and dissociate from the enzyme:

    • This form of inhibition is the primary mechanism of enzyme regulation, employed by cellular regulators and pharmaceuticals.

    • Two main types of reversible inhibitors are:

    • Competitive Inhibition: The substrate (S) competes with an inhibitor (I) to bind to the enzyme (E). More substrate concentration is needed to achieve the same reaction velocity with a competitive inhibitor present.

    • Non-competitive Inhibition: does ot affect S binding, only blocks P formation

6.10 Competitive Inhibition Plots

  • Under competitive inhibition, the Lineweaver-Burk plot shows:

    • Inhibition leads to an increase in Km but Vmax remains unchanged. This is due to the need for a higher substrate concentration to achieve half-maximal velocity, demonstrating that the inhibitor competes with the substrate for the same active site.

6.11 Noncompetitive Inhibition Plots

  • In non-competitive inhibition, the maximum velocity (Vmax) of the system decreases as the presence of non-competitive inhibitors affects the flow of product formation. The Km value does not change because the substrate binding is not obstructed.


6.13 Irreversible Inhibition

  • Irreversible inhibitors: modifying agents are covalently attached, rendering them inactive:

    • Cannot be removed

    • Leaving enzyme with little to no activity