Enzymology Glossary

The minimum energy required for reactants to reach the transition state and undergo a chemical reaction. Enzymes lower this barrier.

The specific region of an enzyme where substrate binding and catalysis occur.

A regulatory site on an enzyme, distinct from the active site, where effector molecules bind to modulate activity.

The protein component of an enzyme that requires a cofactor for activity, without its cofactor.

The ratio kcat/Km, which measures how effectively an enzyme converts substrate to product at low substrate concentrations.

A non-protein chemical compound required by an enzyme for its catalytic activity, including metal ions and organic coenzymes.

A molecule that competes with the substrate for binding at the active site of an enzyme.

The phenomenon in multi-subunit enzymes where substrate binding at one site influences binding affinity at other sites.

The loss of an enzyme's three-dimensional structure and catalytic activity due to heat, extreme pH, or chemical agents.

A biological macromolecule, typically a protein, that catalyzes a specific chemical reaction.

A regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.

The complete, catalytically active form of an enzyme consisting of the apoenzyme plus its required cofactor(s).

An enzyme that catalyzes the cleavage of bonds by the addition of water (EC class 3).

Different forms of the same enzyme that catalyze the same reaction but differ in amino acid sequence and kinetic properties.

An enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate molecule.

A double reciprocal graph of 1/V vs. 1/[S] used to determine Km and Vmax and to distinguish types of enzyme inhibition.

The substrate concentration at which the reaction velocity is half of Vmax; a measure of enzyme-substrate affinity.

An enzyme that catalyzes oxidation-reduction reactions, transferring electrons between molecules (EC class 1).

An enzyme that catalyzes the hydrolysis of peptide bonds in proteins.

An RNA molecule capable of catalyzing a chemical reaction, demonstrating that catalysis is not exclusive to proteins.

The ratio kcat/Km, representing the overall efficiency of an enzyme in converting substrate to product.

The molecule upon which an enzyme acts, binding to the active site to be converted into product(s).

The highest-energy, most unstable intermediate along the reaction coordinate between substrate and product.

The maximum number of substrate molecules converted to product per enzyme active site per unit time.

An inactive enzyme precursor that requires a biochemical change, typically proteolytic cleavage, to become active.