BackGOB Chemistry: Enzyme Classification & Regulation
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Terms in this set (22)
An enzyme is a biological catalyst, typically a protein or RNA, that speeds up biochemical reactions. Enzyme names usually end in "ase" and are named after their substrate.
The substrate is the reactant molecule upon which an enzyme acts to form a product.
The 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 vitamins or their derivatives, involved in redox reactions.
An apoenzyme is the protein part of an enzyme without its cofactor/coenzyme. A holoenzyme is the catalytically active enzyme with its cofactor/coenzyme bound.
Enzymes speed up reactions by proximity effect, orientation effect, lowering activation energy via energy effect, and providing catalytic functional groups.
The energy effect lowers activation energy by inducing strain on substrate bonds, facilitating the reaction.
Oxidoreductases, Transferases, Hydrolases, Isomerases, Lyases, and Ligases.
Oxidoreductases catalyze oxidation-reduction reactions involving electron transfer.
Dehydrogenases remove two hydrogen atoms from a substrate to form a double bond, requiring coenzymes like FAD or NAD+.
Transferases transfer functional groups such as amino or phosphoryl groups between substrates.
Kinases transfer phosphoryl groups; transaminases transfer amino groups.
Hydrolases catalyze hydrolysis, breaking bonds by adding water.
Lipases (ester bonds in lipids), Proteases (peptide bonds), Nucleases (phosphate ester bonds in DNA/RNA), Amylases (1,4 glycosidic bonds in starch).
Isomerases catalyze rearrangement of atoms within a molecule to form isomers.
Lyases add or remove small molecules to/from double bonds, often forming or breaking double bonds.
Ligases catalyze bond formation between molecules coupled with ATP hydrolysis.
Specific enzymes catalyze one reaction for a single substrate; nonspecific enzymes catalyze one reaction for a group of similar substrates.
The induced fit model states substrate binding causes a conformational change in the enzyme, improving binding and catalysis.
Enzyme activity increases with temperature up to an optimum, beyond which activity decreases due to denaturation.
Each enzyme has an optimum pH; activity decreases if pH deviates from this optimum.
Increasing substrate concentration increases rate until saturation; increasing enzyme concentration increases rate if substrate is in excess.