Enzyme Kinetics and Inhibition Quiz

Enzyme Kinetics and Inhibition

• Enzyme classifications include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
• Enzymes lower activation energy (Ea) to increase reaction rate without changing thermodynamic parameters.
• The Michaelis-Menten equation relates substrate concentration to Vmax and KM, with Vmax representing maximal velocity and KM the Michaelis constant.
• Saturation kinetic curve shows enzyme saturation with substrate and the impact of high or low KM values.
• Lineweaver-Burke plot provides a double reciprocal of the Michaelis-Menten equation, offering an easier method for interpreting graphical data.
• Turnover number (kcat) measures the number of reactions an enzyme can catalyze per unit of time, indicating catalytic efficiency.
• Diffusion controlled limit occurs when the rate-limiting step becomes the diffusion of enzyme and substrate, with a rate between 108 and 109 M−1 sec−1.
• Inhibitors can be irreversible or reversible, preventing the generation of products.
• Suicide inhibitors irreversibly block enzyme function by covalently modifying the active site, examples include pesticides and nerve agents.
• Competitive inhibition involves molecules similar to the substrate shape, competing directly with the substrate and can be overcome with high substrate concentration.
• Uncompetitive inhibition binds to the ES complex, decreasing both Vmax and KM.
• Mixed inhibition combines features of competitive and uncompetitive inhibitors, being effective regardless of substrate concentration.

Enzyme Catalysis and Regulation

• Carbonic anhydrase is found in erythrocytes and catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site.
• Proteases are enzymes that degrade proteins and include trypsin, chymotrypsin, and elastase, and are important in protein maturation, blood clotting, and protein trafficking.
• Different classes of proteases, including serine, aspartyl, metallo-, and cysteine proteases, employ similar chemistry with conserved topology and overall structure.
• Chymotrypsin is a serine protease that cleaves dietary protein and contains a catalytic triad with Aspartate, Histidine, and Serine.
• Affinity labeling is a technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone.
• Enzyme regulation can be achieved through altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification and allosteric regulation methods.
• Covalent modification involves the covalent addition or removal of groups from proteins, with proteolytic cleavage and phosphorylation as common means of activation.
• Zymogens are inactive enzyme precursors that require proteolytic activation, with chymotrypsinogen being the inactive form of chymotrypsin.
• Phosphorylation is another example of protein activation facilitated by protein kinases adding phosphate groups and phosphatases removing them, regulated through signaling cascades.
• Src is an example of regulation via phosphorylation.
• Allosteric regulation can increase or decrease enzymatic activity by binding at a site other than the active site, with relaxed (R) and tense (T) states and sigmoidal activity curves.
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Test your knowledge of enzyme kinetics and inhibition with this quiz. Explore topics such as Michaelis-Menten equation, turnover number, saturation kinetic curve, Lineweaver-Burke plot, and various types of enzyme inhibitors including competitive, uncompetitive, and mixed inhibition.