Biochemistry - Enzymes

Biochemistry - Enzymes

1. Made up of only protein

2. Protein + bound non-protein component

   • Protein alone: apo-enzyme Complete enzyme: holo enzyme
   • Non protein component that is always bound: prosthetic group
   • Non protein component that is only bound for action: co-enzyme

3. Rate vs. Conc graph (with enzyme) - hyperbolic

   • Michaelis-Menten equation: v = Vmax [S] / Km + [S]
     • Lineweaver-Burke Plot: 1/v vs. 1/[S] y-intercept: 1/Vmax x-intercept: -1/Km Error is exaggerated (because inverse is being taken)
     • Eadie-Hofstee Plot: v vs. v/[S] y-intercept: Vmax slope: Km error distribution is more evenly spread (and not vertical because there are two variables plotted along the x-axis
   • E + S <-> ES -> E + P
   • Acc. (Km) - equil. constant for S binding to E
   • Vmax - max. rate at which enzyme can operate

4. Enzyme Inhibition

   • Competitive Inhibition: Inhibitor competes with substrate for active site. v = Vmax [S] / [S] + Km(1+Ki) Km is altered
   • Uncompetitive Inhibition: Inhibitor can only react with a site made accessible on ES complex (ternary complex). v = {[S] Vmax}/(1+[I]/Ki)} / {[S]+ Km/(1+[I]/Ki)} both Km and Vmax are altered
   • Non-competitive Inhibition