Enzymes 2 Flashcards
Define isozymes.
Different proteins which catalyse the same reactions i.e glucokinase and hexokinase.
What reaction do glucokinase and hexokinase catalyse?
Glucose + ATP -> Glucose-6-Phosphate +ADP + Pi
What does a high Km mean?
Low affinity for substrate and a slower reaction. (Glucokinase).
What does a low Km mean?
High affinity for substrate and a faster reaction. (Hexokinase).
What can it mean if enzymes are found in the wrong place?
It means there is cell damage and there may be a leakage of enzymes into the bloodstream.
Define ternary complex.
An enzyme with 2 or more substrates bonded to it.
Do allosteric enzymes follow M-M kinetics?
No
Allosteric enzymes are…
Made up of many subunits which contain many active sites.
What 3 things will affect an enzyme?
Increased temperature (increase molecule collisions, increase molecule energy but will eventually denature) pH (changes charges of amino acids, extremes can denature, affects substrates which may need a hydrogen or hydroxide ion group) Inhibitors
Define a competitive inhibitor.
Mimics the substrate. Binds to the active site stopping the substrate from being able to bind.
Bind non-covalently. Decrease affinity between active site and substrate so Km increases.
Define an uncompetitive inhibitor.
Bind near the active site and block the product leaving the active site.
Define a noncompetitive inhibitor.
Binds at another point of the protein, altering the active site.
Bind non-covalently. Substrate can usually bind to active so Km remains constant but an increase in substrate concentration will do nothing so Vmax decreases.
Define transition state analogues.
Inhibitor mimics the transition state instead of the substrate. Hard to isolate as they are an intermediate step.
Define catalytic antibodies.
Can be generated against potentially any biological molecule and therefore are made specifically for transition state molecules.
What makes an irreversible inhibitor irreversible?
Bind covalently.
