Enzymes Flashcards
What is an enzyme?
A substrate produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction. It increases reaction rates, and they can be compared based on rate of enhancement.
What is a catalyst?
It changes the rate of reaction without net change of catalyst itself (increase reaction rates without being consumed; do not alter equilibrium) (ex: enzymes)
How is enzyme activity regulated?
pH, temperature (high temp increases function), enzyme concentration, substrate concentration, cofactors and coenzymes
What are cofactors and coenzymes?
1/3 of all known enzymes require metal ions, and they help with binding enzymes and substrate .
What does Vmax mean?
rate of formation of bonds inherit to number of enzymes. it is inherent to the number of enzyme molecules.
What does Km mean?
it is the measure of breakdown of Enzyme-Substrate (Km = [E] [S] / [ES]). It is a measure of how tightly an enzyme binds its substrate. (small Km means tight binding, and high Km indicates weak binding).
What is kcat?
Number of enzyme turned product (kcat = Vmax / [E]) (units s-1)
What is the Michaelis-Menton equation?
V0 = Vmax + [S] / Km + [S]
Describe irreversible suicide enzyme inhibitors.
When an inhibitor binds permanently to an enzyme and impairs the enzyme, eventually killing it.
Describe competitive inhibition
When an inhibitor binds to an active site. Km will be increased because it will need more substrate to outweigh the competitive inhibitor but Vmax will remain unchanged because it does not change the amount of substrate to enzyme.
Describe uncompetitive inhibition
When inhibitor binds to enzyme-substrate complex (enzyme has to bind to substrate first). No added amount of substrate will change Vmax, so Vmax will go down and so will Kd.
Describe noncompetitive inhibition.
inhibitor binds to enzyme substrate complex or active site. adding more substrate does not change the Vmax. Vmax will be lowered but Km will remain constant.
Describe mixed inhibition.
Most common type where Km could be either increased or lowered. Inhibitor has affinity for one or the other. If affinity for [ES] = Vmax will go down and Km will decrease. If affinity for [E] = Vmax will decrease and Km will increase.
