U or enzyme activity unit

A unit of enzyme activity adopted in 1964 by the International Union of Biochemistry,1 having been defined by its Enzyme Commission in 1961.2 One unit is the amount of enzyme activity which will catalyse the transformation of 1 micromole of the substrate per minute under standard conditions. The unit was not given a name. Symbol, U.

This unit was replaced in 1978 by the katal. 1 U corresponds to 16.67 nanokatals.

International Union of Biochemistry.
Enzyme Nomenclature: Recommendations 1964 of the International Union of Biochemistry.
Amsterdam: Elsevier, 1965.

See Chapter 4.

International Union of Biochemistry.
Report of the Commission on Enzymes.
Oxford: Pergamon Press, 1961.

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