Enzymes Flashcards
What is an enzyme?
A specific protein that speeds up the rate of a reaction by lowering the activation energy of a reaction.
- They are not changed or consumed in the reaction
- are sensitive to temperature and pH
- do not affect equilibrium
- do not change thermodynamic parameters (G, S, H)
What is the structure of an enzyme?
- scaffolded for support and position the active site
- then the active site has a binding site and a catalytic site
Catalytic site
Part of enzyme that is very specific and where the reaction is catalyzed
Binding site
Where the substrate interacts with enzyme through intermolecular interactions
Positions the substrate so it is properly in the catalytic site
Substrate
What is being changed by the enzyme
Ligand
Any Substance enzyme interacts with - encompasses both substrate and regulatory molecules
Orthosteric Regulatory Elements
Interact with enzyme at its active site
Allosteric Regulatory Elements
Bind/interact with enzyme at some other place, other than the active site
Induced fit model
Enzyme and substrate affect each other
-initial binding undergoes conformational shifts that allow closer binding and more efficient catalyst
Lock and key
Substrate fits into enzyme like a key to a lock - perfect fit with no changes in structure to get a better fit
This is inadequate to explain enzymes interactions with their substrates
Oxidoreductases
Catalyze oxidation/reduction reactions
Ex: alcohol dehydrogenase, superoxide dismutase
Transferases
Transfer fictional group between molecules
Ex: aspartame transaminase
Creatine kinase
DNA polymerase
Hydrolases
Catalyze hydrolysis
Ex: angiotensin converting enzyme
Pancreatic lipase
Lactase
Isomerases
Catalyze isomerization
Ex: Ribose-5-phosphate isomerase
Ligases
Join molecules together with covalent bonds
Ex: aminoacyl tRNA synthetase
Glutamine synthetase
Pyruvate carboxylase
Kinase
Adds a phosphate group to a molecule (phosphorylates
Phosphatase
Removes a phosphate