BackGOB Chemistry - Enzyme Classification & Regulation
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Terms in this set (20)
An enzyme is a biological catalyst, usually 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 metals) required for enzyme activity; coenzymes are organic cofactors, often vitamins or derivatives, involved in redox reactions.
Apoenzyme is the protein part of an enzyme without its cofactor; holoenzyme is the active enzyme with its cofactor or coenzyme bound.
Enzymes catalyze by proximity effect, orientation effect, lowering activation energy via strain (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 (bond cleavage with water). Subclasses include lipases, proteases, nucleases, and amylases.
Isomerases catalyze 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 explains substrate binding causes conformational changes in the enzyme, improving specificity and catalysis.
Enzyme activity increases with temperature up to an optimum, then decreases due to denaturation.
Each enzyme has an optimal pH; deviations can reduce activity by altering enzyme structure or charge.
Increasing substrate concentration increases reaction rate until enzyme saturation is reached, then rate plateaus.
Increasing enzyme concentration increases reaction rate linearly if substrate is in excess.
The active site is the enzyme pocket where substrate binding and catalysis occur.