Backlecture 10
2:14
Terms in this set (20)
An enzyme is a biological catalyst, typically a protein or RNA, that speeds up biochemical reactions without being consumed.
A substrate is the reactant molecule upon which an enzyme acts to form a product.
Turnover number is the number of substrate molecules converted to product by an enzyme per unit time.
Cofactors are nonprotein substances (often trace metals) required for enzyme activity. Coenzymes are organic cofactors, often vitamin derivatives, involved in redox reactions.
Apoenzyme is the protein part of an enzyme without its cofactor/coenzyme. Holoenzyme is the catalytically active enzyme with its cofactor/coenzyme bound.
Enzymes lower activation energy by proximity effect, orientation effect, inducing strain on substrate bonds (energy effect), and providing catalytic functional groups.
Oxidoreductases, Transferases, Hydrolases, Isomerases, Lyases, and Ligases.
Oxidoreductases catalyze oxidation-reduction reactions involving electron transfer.
Kinases transfer phosphoryl groups; Transaminases transfer amino groups between substrates.
Hydrolases catalyze hydrolysis reactions. Subclasses include lipases (lipid ester bonds), proteases (peptide bonds), nucleases (DNA/RNA phosphate bonds), and amylases (glycosidic bonds).
Isomerases catalyze the rearrangement of atoms within a molecule to form isomers.
Lyases catalyze addition or removal of small molecules to/from double bonds without hydrolysis or oxidation.
Ligases catalyze bond formation between two molecules coupled with ATP hydrolysis.
Specific enzymes catalyze one reaction for a single substrate. Nonspecific enzymes catalyze a reaction for a group of similar substrates.
The induced fit model describes substrate binding causing conformational changes in the enzyme, improving specificity and catalysis, unlike the rigid lock-and-key model.
Enzyme activity increases with temperature up to an optimum, beyond which activity decreases due to denaturation.
Each enzyme has an optimal pH; deviations can reduce activity by affecting enzyme structure or ionization of active site residues.
Increasing enzyme concentration increases reaction rate linearly if substrate is in excess.
Increasing substrate concentration increases reaction rate until enzyme saturation, where rate plateaus at maximum velocity.
The triad activates serine to attack peptide bonds, histidine donates a proton to break the bond, and aspartate stabilizes histidine, facilitating catalysis.