Term 1- Lec 10- Enzymes Flashcards
The 6 types of enzymatic reactions
Hydrolases, Ligases, Lyases, Oxidoreductases, Transferases, and Isomerases
Hydrolases
Cleave bonds by the addition of water
Ligases:
Form bonds between C and O, S, and N coupled with hydrolysis of high energy phosphates
Lyases:
Cleave C-C, C-S, and certain C-N
Oxidoreductases:
Catalyse oxidation-reduction reactions
Transferases:
Transfer C-, N- and P- containing groups
Isomerases:
Catalyze racemization of optical or geometric isomers
Cofactor
A small molecule required for the catalytic activity of an enzyme
Coenzyme
An organic cofactor ie. vitamins
Cosubstrate
When the cofactor only transiently binds to the enzyme
Prosthetic group
When the cofactor is permanently associated with the enzyme, either covalently or non-covalently
Holoenzyme
Catalytically active enzyme-cofactor complex
Apoenzyme
Inactive protein lacking the cofactor
Glycopeptidyl Transferase (GT)
Penecillin acts as a competitive inhibitor and covalently binds the active site, rendering it useless
Catalysis by proximity
Enzyme creates local high concentration of substrates and orients them correctly for bonding
Covalent catalysis
Enzyme forms a transient covalent bond with the substrate (typical in transferases)
Catalysis by strain
Binds the substrate and puts it in an unfavor position to weaken the bond, making it easier to break the bond
Mechanism for general acid-base catalysis
Side chains or prosthetic groups mediate proton transfer/binding between E and S/T
Effect of substrate concentration on rxn rates
The rxn rate increases with concentration increase until it reaches a maximum level of saturation.
Effect of enzyme concentration on rxn rates
More enzyme = faster rate
effect of pH on rxn rate
environmental pH can strongly affect a rxn rate, with every enzyme having it’s own optimal pH for functioning
Effect of denaturation on rxn rate
Denaturation causes enzymes to lose shape, thus function. pH, temperature, heavy metals, organic solvents, or mechanical mixing can cause it
Effect of temperature on rxn rate
High temperatures increase chances of molecular colisions. At a certain high temperature, proteins begin to denature though. Low temps slow rxns.
What does stereospecificity mean in enzymes?
They can tell D and L enantiomers apart and will only bind to one enantiomer of a molecule.
