Enzyme unit

Unit of catalytic activity

The enzyme unit or international unit (symbol U or IU) is a unit measuring an enzyme's catalytic activity. An enzyme unit is defined as the amount of the enzyme that catalyzes the conversion of one micromole (μmol) of substrate per minute (min) under the specified conditions of the assay method. The specified conditions will usually be the optimal conditions—including but not limited to temperature, pH, and substrate concentration—which yield the maximal substrate conversion rate for that particular enzyme.

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