Unit 2 Terms Flashcards
cofactors
provide additional chemistries for carrying out catalysis
transition state
is a barrier to chemical reactions
apo-enzyme vs holo-enzymes
apo-enzyme: without cofactor
holo-enzymes: with cofactor
Nucleophiles
attack electron-deficient centers to create covalent bonds
Metal ions as catalysts
mediate oxidation-reduction reactions, promote reactivity of the substrate or other functional groups
Isozymes
Two different enzymes that catalyze the same reaction
A unimolecular reaction
has a velocity (rate; v) that is dependent on
the concentration of only one substrate
k A------>P
A bimolecular (second order) reaction
has a velocity that is dependent on two substrate concentrations
k A + B------>P
Initial reaction velocity
only depends on the rate determining step
see lecture 10 slides 6-7
Catalytic efficiency
reflects both enzyme rate (kcat) and substrate affinity (KM), and is measured by kcat/KM
note:
- it also indicates the preferred substrate of an
enzyme
Enzyme inhibitors
prevent enzyme catalysis and are important in medicine, biotechnology, and research
Reversible inhibitors
- reversible inhibitors can be classified by where they bind and their effects on enzyme kinetics
- competitive, non-competitive, uncompetitive
- bind to enzymes non-covalently
Competitive inhibitors vs non-competitive inhibitors
Competitive:
- With competitive inhibition Km is increased, Vmax is unchanged
Non-competitive
- appear to decrease Vmax
- S (substrate) and I (inhibitor) are not mutually exclusive, but ESI complex is less active than ES (allostery)
Mixed inhibition
Similar to non-competitive inhibition, but binding to
distant site modifies both Vmax (reduced) and Km (Increased)
Passive transport vs Active transport
- Passive transport occurs without energy input
- Active transport requires energy input
