Enzyme as Catalysts Part 2 Flashcards
which step is the rate limiting step
product formation step or K3
when the enzyme is fully saturated with substrate
operating at Vmax, K3 is called the catalysis rate of Kcat.
What is Km
Km is the substrate concentration at half of Vmax
Describe the relationship between Km and affinity
The higher the Km is the lower the affinity and vice versa
Describe the relationship between hexokinase and glucokinase
Glucokinase has a lower affinity because it is found in the liver and the liver has a large abundance of glucose. However once glucose is passed out of the liver to the rest of the body it is very sought after. This is where hexokinase comes in and it doesn’t want to waste its opportunity to utilize the limited glucose so it has a much larger affinity for it then glucokinase.
How to read lineweaver burk plot
It is a double reciprocal of a michaelis menton plot. Read the Km on the x-axis as the same. Right increase left decrease. But the y axis which represents v-max goes down when it increases and up when it decreases.
describe the km and vmax for competitive and non-competitive inhibition
Competitive- Km increases but Vmax stays the same
Non-competitive-Km stays the same but Vmax decreases
Describe Multi-Substrate Reactions
Whatever has the lowest concentration will be the rate limiting reagent. So as that reagent increases in concentration the rate of the reaction will increase.
What will be the strongest bond between an enzyme and a substrate or inhibitor.
Whatever has the strongest affinity for the transition state.
Mechanism-based or covalent inhibitors
an inhibitor that binds to an amino acid in the active site covalently and its irreversible. It destroys the active site and is also called suicide inhibitors.
Example of mechanism based or covalent inhibition
cyclooxygenase and aspirin
cyclooxygenase produces prostaglandins that signal for pain and fever
Aspirin can inhibit this process by acetylating a serine residue in the active site of COX
Non-covalent irreversible inhibitors
They resemble the transition state so they bind the enzyme with extremely high affinity and never let go
example of non-covalent irreversible inhibitor
HIV inhibitor drugs can inhibit HIV protease so HIV can no longer snip proteins in our cells and use them for their own survival
