Enzyme unit 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 The enzyme unit should not be confused with the international unit (IU); although it is true that both measure chemical activity and that for many enzymes 1 U = 1 IU (because for many enzymes the existing U was adopted as the newer IU), international units can be defined for the biologic activity of
Amount of substance the molar mass. Molar quantities are sometimes denoted by a subscript Latin "m" in the symbol, e.g. "C", molar heat capacity at constant pressure: the subscript may be omitted if there is no risk of ambiguity, as is often the case in pure chemistry. The main derived quantity in which amount of substance enters into the numerator is amount of substance concentration, "c". This name is often abbreviated to "amount concentration", except in clinical chemistry where "substance concentration" is the preferred term to avoid ambiguity with mass concentration. The term "molar concentration" is incorrect, but commonly used. The alchemists, and