Enzyme Catalysis Flashcards
What is the mass range for enzymes?
10 kDa –> 1000 kDa
How fast do enzymes accelerate reactions?
They accelerate reactions by a factor of 10^6 or more
I.e.:
1) Carbonic anhydrase 7.7 x 10^6
2) Triose phosphate Isomerase 1.0 x 10^9
3) OMP decarboxylase 1.4 x 10^7
What are cofactors?
Small non-protein molecules that bind to many enzymes and facilitate their catalytic activity
Holoenzyme
with cofactor
ACTIVE
Apoenzyme
Without cofactor
INACTIVE
Inorganic cofactors
Metal Ions
Examples:
1) Carbonic anhydrase- Zn2+
2) Hexokinase- Mg2+
Organic cofactors
Derived from vitamins
Called coenzymes
What are the two types of coenzymes?
1) Co-substrate
- loosely bound
- changed by the reaction
- i.e.: lactate dehydrogenase NAD+ (from niacin)
- can be used by an enzyme and then re used
2) Prosthetic group
- Tightly or covalent lay bound
- not changed by the reaction
- monoamine oxidase FAD (from riboflavin)
What is the job for proteases?
Hydrolyzes peptide bonds
-also hydrolyzes closely related ester bonds
Papin
Cleaves any peptide bond
Trypsin
Splitting peptide bonds only on the carboxyl side of lysine and arginine residues
Thrombin
very specific
Hydrolyzes arginine-glycine bonds in particular peptide sequences
Free energy change
DeltaG= Gp- Gr
- independent of the path that is followed in converting reactants to products
- only considers initial and final states
- give no info about rate/kinetics of reaction
- gives info about spontaneity of reaction
ΔG
Spontaneous Exergonic
ΔG > 0
Not spontaneous endergonic
ΔG = 0
Equilibrium
Equilibrium conditions
ΔG= 0
ΔG˚’= -RTlnK’eq
ΔG˚’
Standard free energy change for given reaction at standard conditions of:
P=1 atm
[X]= 1 M
PH= 7
No actual standard temperature, ΔG˚’ just determined at the temp of the system