Enzymes Flashcards
Enzymes
Protein catalysts that increase the velocity of a chemical reaction without being changed or consumes by the reaction
Holoenzyme
Active enzyme including its non protein component
Apoenzyme
The enzyme without the non-proteic component and is inactive
Co-factor
Metal non- proteic component of an enzyme
Co-enzyme
An organic component of an enzyme
Co-substrates
Co-enzymes transiently associating with the enzyme are called substrates
Prosthetic group
A co-enzyme permanently associated with the enzyme
Factors affecting reaction velocity
Substrate concentration, temperature and pH
Rate of a reaction
The number of substrate molecules converted to product per unit time - expressed as micro moles of product per minute
Increasing substrate concentration
Increases the rate of an enzyme-catalysed reaction until a given rate is reached
Vmax
Reflects saturation of all available binding sites on the enzyme with the enzyme
Effect of temperature
Increases results in increase in rate as more molecules have enough energy to pass over the energy barrier
Further increase decreases velocity as enzyme becomes denatured as hydrogen bonds break inactivating the protein
Effect of pH
Extremes denature proteins and enzymes
Optimum pH
pH at which velocity is at its greatest
Specific for every enzyme and reflects its specific function
Ways to regulate enzyme activity
Covalent modification
Induction/repression of enzyme synthesis
Allosteric regulation
Effectors
Regulate enzymes by binding non covalently to a site other than the active site
Can function as negative of positive regulators
Can alter the affinity of an enzyme for its substrate or modify the maximal catalytic activity of the enzyme
Feedback inhibition
When an increase in concentration of an end product will inhibit an enzyme catalysing a reaction earlier in the metabolic pathway
Regulation of enzymes by covalent modification
Usually by addition or removal of phosphate groups from specific serine, threonine and less frequently tyrosine residues
Induction of enzyme synthesis
Enzyme activity can be regulated by changes in enzyme synthesis - more enzymes means more active sites available for reaction
Repression of enzyme synthesis
By enzyme degradation
