MBIO 2360 Lecture Notes - Lecture 12: Ribose, Glyceraldehyde, Xylose
1 Dec 2016
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Document Summary
Vo vs. [s] plot is sigmoidal whereas m-m plots are hyperbolic. The enzyme will be very sensitive to [s] over a narrow range and behaves like an on-off switch. The nonmm behaviour arises in multisubunit enzymes where the occupancy of an active site on one subunit has an effect on the other subunits. The substrates binding to one active site on one subunit causes an effect on another active site to make it have a higher affinity for substrate. The binding of s to one active site of the enzyme makes the binding of subsequent s easier. First, each subunit can exist in 2 conformations: Without s, the equilibrium favours t and weak binding. Binding of s stabilizes the r state pulling the equilibrium to the high affinity form simply by the law of mass action. Increasing the amount of r state creates more affinity sites and results in more s binding, until the enzyme is saturated.
