Enzymes Flashcards
The transfer of electrons between biological molecules (oxidation-reduction rxns) are catalyzed by which enzymes?
Oxidoreductases
-Reductant: e- donor
-Oxidant: e- acceptor
Ex: dehydrogenase, reductase, oxidase
The movement of functional groups from one molecule to another are catalyzed by?
Transferases
-Kinases are part of this class (responsible for catalyzing transfer of phosphate group from ATP to another molecule)
The breaking of a compound into two molecules by the addition of H2O is catalyzed by which enzymes?
Hydrolases
-Ex: phosphatase, peptidase, nuclease, lipase, and etc.
A single molecule being cleaved into 2 products is carried out by which enzymes?
Lyases
-also carries out synthesis of 2 molecules into a single one (synthases)
The rearrangement of bonds within a molecule are catalyzed by-?
Isomerases
-Catalyze rxns between stereoisomers and constitutional isomers
The synthesis/addition of similar large molecules are catalyzed by which enzymes?
Ligases (often requires ATP)
-Nucleic acid synthesis and repair
Some enzymes require non-protein molecules to catalyze a rxn called…?
Coenzymes & cofactors
- Usually kept @ low conc. in cells
- Enzymes w/o: apoenzymes
- Enzymes w/: holoenzymes
- Prosthetic groups: tightly bound cofactors/coenzymes that are necessary for enzyme function
Inorganic molecules or metal ions that are generally digested as dietary minerals are?
Cofactors
Small organic groups of vitamins or vitamin derivatives are?
Coenzymes
What is the only way to increase vmax?
Increase enzyme conc
-Induce expression of gene encoding the enzyme
When the rxn rate is = to 1/2 vmax…?
Then Km = [S]
The [S] conc at which half the [E]’s active sites are full is referred to as?
Km (michaelis constant)
- Can be a measure of affinity of an enzyme for its substrate
- Intrinsic property=cannot be altered/changed by changes in conc of enzyme and substrate
When [S]
Changes in substrate conc will greatly affect the rxn rate
When [S]>Km….?
Changes in substrate conc increase much more slowly as it approaches vmax
The # of substrate molecules converted to product per enzyme molecule per second is termed?
Kcat
-Typically between 101-103
Catalytic efficiency of an enzyme refers to the ratio of…?
Kcat/Km
-Large Kcat or small Km will result in higher catalytic efficiency (more efficient enzyme)opii
If Hill’s coeff>1…?
Positive cooperative binding is occuring
-After 1 ligand is bound, the affinity of the enzyme for further ligands increases
If Hill’s coeff<1…?
Negative cooperation binding occurs
-After 1 ligand is bound, the affinity for the enzyme for further ligands decreases
If Hill’s coeff=1…?
The enzyme doesn’t exhibit cooperative binding
Inhibition that involves the occupancy of an enzyme’s active site that can be overridden by adding more substrate is termed?
Competitive Inhibition
- Vmax: no effect
- Km: is increased
Inhibition to the allosteric site of an enzyme that causes an irreversible conformational change is termed?
Noncompetitive Inhibition
- Vmax: decreased (less enzyme available to react)
- Kmax: no effect
When an inhibitor can bind to an enzyme and enzyme substrate complex, but have different affinity for each is termed?
Mixed inhibition
- Bind on allosteric site
- Km effect varies
- Vmax: decreases
Inhibitors that bind only to the enzyme substrate complex and essentially lock the substrate in the complex, preventing its release is termed?
Uncompetitive inhibition
-Vmax and Km: decreases
Enzymes that have more than one binding site are termed?
Allosteric enzymes
-Alternate between active and inactive form
