<P> The enzyme unit (symbol U or sometimes EU) is a unit for the amount of a particular enzyme . </P> <P> One U is defined as the amount of the enzyme that produces a certain amount of enzymatic activity, that is, the amount that catalyzes the conversion of 1 micro-mole of substrate per minute . The conditions also have to be specified: one usually takes a temperature of 25 ° C and the pH value and substrate concentration that yield the maximal substrate conversion rate . </P> <P> The enzyme unit was adopted by the International Union of Biochemistry in 1964 . Since the minute is not an SI unit, the enzyme unit is discouraged in favour of the katal, the unit recommended by the General Conference on Weights and Measures in 1978 and officially adopted in 1999 . One katal is the amount of enzyme that converts 1 mole of substrate per second, so </P> <Dl> <Dd> 1 U = (1 / 7006100000000000000 ♠ 1000000) / 60 × 1 kat = 1 / 60 μkat, and thus </Dd> <Dd> 1 U = 16.67 nkat </Dd> </Dl>

What is a u (or unit) of an enzyme equivalent to