Chem 153A Enzyme Kinetics & Inhibition PDF

CHEM 153A – Enzyme Kinetics and Enzyme Inhibition Quiz Content Enzyme kinetics Enzyme kinetics is the study of the rates of enzymatic reactions. Michaelis-Menten enzyme kinetics (MM kinetics) is a basic set of assumptions about the behavior of enzymes with reference to the concentrations of the co...

CHEM 153A – Enzyme Kinetics and Enzyme Inhibition Quiz Content Enzyme kinetics Enzyme kinetics is the study of the rates of enzymatic reactions. Michaelis-Menten enzyme kinetics (MM kinetics) is a basic set of assumptions about the behavior of enzymes with reference to the concentrations of the compounds they act upon, enzyme substrates. The following is the equilibrium reaction used by MM: (E is enzyme, S is substrate, ES is bound enzyme-substrate, P is product) From this, MM derived the following equation, which describes the production rate of enzymes, v, the maximum possible production rate, Vmax, and Km, which is equal to the [S] which permits the enzyme to achieve ½ Vmax: Plotting this equation against [S] and plotting its inverse against 1/[S] we get the following plots: Michaelis-Menten plot Lineweaver-Burk plot Enzyme inhibition Enzyme inhibitors are compounds that interfere with substrate binding or catalysis, slowing or halting enzymatic reactions. For this quiz we’ll be focusing on four types of reversible inhibition, i.e. inhibition that takes the form of reversible binding as opposed to chemical modification. This means that this kind of inhibition can be described by equilibria like E + I ⇋ EI, which has the equilibrium constant KI (where KI = [E][I]/[EI]) On the next two pages are the four types of reversible inhibition along with the key features you need to know… Competitive inhibition Competitive inhibitors compete with the substrate for the active site of an enzyme (non-allosteric) - Enzyme-inhibitor reaction and equilibrium - Lineweaver-Burk plot and inhibition impacts Km increased Vmax unaffected Uncompetitive inhibition Uncompetitive inhibitors bind at a site distinct from the substrate active site (allosteric inhibition), and only bind to the ES complex - Enzyme-inhibitor reaction and equilibrium - Lineweaver-Burk plot and inhibition impacts Km decreased Vmax decreased Mixed inhibition Mixed inhibitors also bind at a site distinct from the substrate active site (allosteric inhibition) but can bind to E or ES - Enzyme-inhibitor reaction and equilibrium - Lineweaver-Burk plot and inhibition impacts IF KI < K’I then Km is increased IF KI > K’I then Km is decreased Vmax decreased Noncompetitive inhibition Noncompetitive inhibitors have the same mechanism of action as mixed inhibitors (also allosteric) but they bind equally to both E and ES - Enzyme-inhibitor reaction and equilibrium KI = K’I - Lineweaver-Burk plot and inhibition impacts Km unaffected Vmax decreased