Properties Of Enzymes And Enzyme Kinetics Flashcards
What’s an enzyme
Biological catalysts which speed up rate of reaction without altering final equilibrium between reactants and products
Consequences of enzyme specificity
- Complex and co-ordinated metabolic pathway
2. Enzyme classification scheme
6 enzyme classes of enzymes
- OXIDOREDUCTASES
- Transferases
- Ligases
- Hydrolases
- Isomerases
- Lyases
What do oxidoreductases do? Example
Add o2 or remove 2H/e-
Lactate dehydrogenase
What do transferases do? Example
Transfer functional group from donors to acceptors
ALANINE AMINOTRANSFERASE
What do lyases do? Example
Catalyse cleavage of C-C, C-O, C-N
ATP-citrate lyase
What do hydrolases do
Hydrolysis.
Trypsin
What do isomerases do? Example.
Catalyse transfer of functional group within same molecule
PHOSPHOGLUCOSE ISOMERASE
What do ligases do? Example
Use ATP to catalyse formation of C-C or C-N bonds
DNA ligase
Chymotrypsin mechanism
- Ppt binds non covalently to side chain of hydrophobic pocket
- H+ transferred from ser to his -> ACYL linkage from ser to ppt-> tetrahedral transition state
- H+ transferred to C-terminal of ppt-> C-N bond of ppt is cleaved-> C-terminal fragment is released
- Water binds to his in place of released ppt
- water transfers H+ to his57 and OH to remaining substrate fragment-> tetrahedral transition state is reformed
- Acyl bond cleaved-> fragment released; H+ transferred back from his to Ser
Example of inorganic element that serves as cofactors
Fe2+
Catalase
Example of co-enzymes
NAD+ with alcohol dehydrogenase
Ethanol + NAD+ -> acetaldehyde + NADH + H+
What are isoenzymes
Enzymes with different protein structures that catalyse Same reaction
Found in different cellular compartments/ different amounts in diff tissues with distinct biochemical roles
