Enzymes 1&2 Flashcards
How are enzymes different from chemicals?
Catalyse very high reaction rates
Regulated by homeostasis
Very specific
Ribozyme
Made from RNA not protein
Cofactor
Non protein component required for activity
Coenzyme
Complex organic molecule made from vitamins eg FAD
Prosthetic group
Cofactor covalently bound to enzyme
Apoenzyme
Protein component of enzyme containing cofactor
Holoenzyme
Whole enzyme apoenzyme + coenzyme
Substrate
Molecule added on by enzyme
Active site
Part of enzyme which substrate binds
How do enzymes reduce Ea
Entropy reduction
Desolvation
Induced fit
Entropy reduction
Molecules randomly come together
Enzyme forces them to collide
Desolvation
Shield of stable water removed
Weak bonds replace these
Km
Substrate concentration at which the initial reaction rate is half of the maximum reaction rate
What does a large km mean?
Unstable
More reversing back
Vmax
How fast a reaction proceeds when enzyme saturated with substrate
Isoenzyme
Different proteins but catalyse the same reaction
Glucokinase
Found in liver
High km and vmax
Hexokinase
Found in other tissues
Low km and vmax
2 ternary examples
Ordered eg pyruvate=>lactate
Random eg creatine=>phosphocreatine
No ternary examples
Amino acid=>keto acid
Ping pong ball
Competitive inhibitors (km and Vmax)
Increased km and unchanged Vmax
Non competitive inhibitors (km and vmax)
Unchanged km and decreased v max
Transition state analogue
Make an inhibitor that mimics transition state
Catalytic antibodies
Antibody with a specific to transition state molecule
Concerted model
Only 2 conformations
Switch between each
Sequential model
No flipping, binding at one subunit causes change in the other subunits
Kinase
Add phosphoryl
Phosphatase
Remove phosphoryl
Proteolytic cleavage
Enzyme exists as inactive precursor which is cleaved to become active
