12 Enzymes - Key Players in Metabolic Pathways Flashcards
Types of enzymes and examples
Oxidoreductases (dehydrogenase, oxidase)
Transferases (kinase)
Hydrogenases (esterase, lipase, amylase)
Isomerases (isomerase, mutase)
Lysases (decarboxylase)
Ligases (DNA ligase, synthetase)
Models of enzyme-substrate interaction
Lock-and-key model
Induced-fit model
Example of induced-fit model
Glucose binding of hexokinase
What are bisubstrate reactions?
enzymatic reactions involving two substrates and giving two products
Factors affecting enzyme catalysis
substrate concentration
enzyme concentration
pH
temperature
Effect of pH in enzyme activity
changes in pH can change the ionization of functional groups in the active site resulting in the loss of activity or even denaturation
Function of regulatory enzymes
catalyses the rate-limiting step in the pathway
Enzyme activity can be regulated by
compounds that bind reversibly to active site
changing the conformation of the active site
changing the concentration of the enzyme
Types of reversible inhibitors
competitive
non-competitive
uncompetitive
Types of regulation through conformational changes
- allosteric activation and inhibition
- covalent modifications (phosphorylation)
- protein-protein interactions
- proteolytic cleavage
Advantages of regulation with allosteric effectors
- much stronger effect on enzyme velocity than inhibitors in the active site
- can be activators as they do not bind to the active site
- can be molecules other than the substrate of the product of the enzyme
- effect is rapid
Principles of covalent modification (phosphorylation)
Addition and removal of a phosphate group on specific serine, threonine or tyrosine residues -> cause conformational changes at the catalytic site by changes in ionic interactions or hydrogen bond patterns
