Enzymes I+II- Lecture 8/31/21 Flashcards
Elastase
A protease that destroys elastin, which destroys the lining of the lungs
How can enzyme activity be deficient
Enzyme isn’t made
Enzyme is made but has a mutation that lowers activity
Insufficient substrate
inhibited
Catalyst
Third party that alters the kinetics of a reaction without being altered itself
Oxidoreductases
Catalyze an oxidation-reduction rxn, ex: NAD+->NADH
Transeferases
Transfer of a chemical group ex: kinases
Hydrolases
Lysis of water, ex: protease
Lyases
A cleavage rxn not using water
Isomerases
Change of a molecular configuration
Ligases
Joining of two compounds ex: DNA poly
Delta G
Change in free energy
Spontaneous rxn
Has a negative delta G
Gibbs free energy equations
DeltaG=DH-TDS
Standard conditions for DGo
Certain temp, 1 M conc, except [H+] is pH of 7
Gibbs free energy in not standard conditions
DG=DGo+RTlnQ
Q
Q= [Products]/[reactants]
Equilibrium
When DG=0
Keq
Q at equilibrium
Keq=e>-DGo/RT
When Q>Keq
The reaction goes in reverse
When Q
Reaction proceeds forward, removal of product drives reaction forward
Transition state
High energy intermediate, stabilization by catalyst allows for the activation energy to be lowered and the rxn to proceed faster
Catabolism
The breakdown of energy yielding nutrients to gain energy in the form of ATP, NADH
Anabolism
Using simple precursor molecules to build complex molecules needed for life, includes active transport and mechanical work
Multibinding enzymes
Enzymes can bind more than one substrate, and often couple an exergonic rxn with an endergonic one
Serine proteases
Proteolytic enzymes that catalyze peptide bond hydrolysis by using activated serine resides to add water and break the bond
Active site
Usually a crevice on the surface of the enzyme where the substrate binds
Velocity of an enzyme
The amount of product formed per unit time
Vmax
The point at which adding more substrate does not lead to an increase in reaction velocity (adding more enzyme increases Vmax)
Equation for velocity
V=Vmax[S]/(Km+[S])
Km
The concentration of substrate when v=1/2Vmax
What does Km tell us about enzyme affinity?
The lower the Km, the higher the affinity
Kcat
A measure of enzymatic efficiency, Kcat=Vmax/the enzyme concentration, “turn over” number. Characteristic of an enzyme
Lineweaver Burke plot
Linear derivation of MM plot, 1/v=(Km/Vmax)1/[S]+1/Vmax
Vmax on LB plot
The Y intercept is 1/Vmax
Km on LB plot
X intercept, -1/km
Competitive inhibitor
Binds in the active site, increases Km but does not effect Vmax
Non-competitive inhibitors
Binds to an allosteric site, Km is unaffective, Vmax is decreased
Zymogens
The active site is not formed correctly until cleavage event
A1-antitrypsin
Inhibits the elastase in the lungs, prevents lung degradation
Protein phosphorylation
Enzymes can be phosphorylated to change the shape and therefore function
Allosteric enzymes
Have t and r state, more sensitive to enzyme concentration
Feedback loops
Final product can inhibit the first enzyme in a pathway
Direct product inhibition
Inhibition of an enzyme by the direct product of that rxn.
