What type of enzyme inhibitor class does Gleevec® fall into? How do you know?
What type of enzyme inhibitor does the light blue triangle represent? How do you know?
What feature of the lemon juice made the difference in preventing apple browning? How did that feature stop the oxidation reaction from occurring?
If apple slices tossed in lemon juice are rinsed in water to remove the lemon juice, would they start to brown again? Would the oxidation reaction still take place? Justify your answer.
Gleevec is a competitive inhibitor, while the light blue triangle represents a noncompetitive inhibitor. Lemon juice contains an enzyme inhibitor that stops the browning of apples by inhibiting the oxidation reaction. Gleevec is classified as a competitive inhibitor because it binds to the active site of the enzyme PDGFR, preventing the substrate PDGF from binding and activating the enzyme. The light blue triangle represents a noncompetitive inhibitor, as it binds to the extracellular binding site of PDGFR, blocking the entry of the normal substrate PDGF without affecting the activation of the enzyme inhibitors. Lemon juice contains an enzyme inhibitor called ascorbic acid, which stops the browning of apples by inhibiting the enzyme responsible for the oxidation reaction. When the apple slices are rinsed in water after being tossed in lemon juice, the oxidation reaction would start again, as the ascorbic acid from the lemon juice would be removed, allowing the enzyme to catalyze the reaction. When rinsed in water, the oxidation reaction can occur again.
Type of Enzyme Inhibitor Class for Gleevec®
Gleevec® falls into the competitive inhibitor class of enzyme inhibitors. This is evident from the fact that Gleevec® binds to the active site of the enzyme PDGFR, specifically blocking the binding of the substrate PDGF. This competitive binding prevents the activation of PDGFR and subsequent initiation of the growth signaling pathways. By directly competing with the substrate for the active site of the enzyme, Gleevec® effectively inhibits the enzyme's function and halts cell growth and division.
Type of Enzyme Inhibitor for Light Blue Triangle
The light blue triangle represents a noncompetitive inhibitor. Unlike competitive inhibitors, noncompetitive inhibitors do not bind to the active site of the enzyme but rather interact with a different site, often causing a conformational change in the enzyme. In the case of the light blue triangle inhibiting PDGFR, it binds to the extracellular binding site of the enzyme, preventing the substrate PDGF from entering and activating the enzyme. This mechanism of action distinguishes it as a noncompetitive inhibitor.
Mechanism of Lemon Juice in Preventing Apple Browning
The feature of lemon juice that prevents apple browning is the presence of an enzyme inhibitor called ascorbic acid, also known as vitamin C. Ascorbic acid inhibits the enzyme responsible for the oxidation reaction that leads to browning in apples. When the apple slices are coated with lemon juice containing ascorbic acid, the enzyme is inhibited from catalyzing the oxidation process, thereby preserving the natural color of the apples.
Effect of Rinsing Apple Slices Tossed in Lemon Juice
If apple slices tossed in lemon juice are rinsed in water to remove the lemon juice, they would start to brown again. Removing the lemon juice also eliminates the ascorbic acid, which was inhibiting the enzyme responsible for the oxidation reaction. Once the ascorbic acid is washed away, the enzyme is free to catalyze the oxidation process, leading to the browning of the apple slices. Therefore, the oxidation reaction would still take place after rinsing the apple slices in water.