Katal


The katal is the unit of catalytic activity in the International System of Units. It is a derived SI unit for quantifying the catalytic activity of enzymes and other catalysts.
The General Conference on Weights and Measures and other international organizations recommend use of the katal. It replaces the non-SI enzyme unit of catalytic activity. The enzyme unit is still more commonly used than the katal, especially in biochemistry.
The katal is not used to express the rate of a reaction; that is expressed in units of concentration per second, as moles per liter per second. Rather, the katal is used to express catalytic activity, which is a property of the catalyst.
The katal is invariant of the measurement procedure, but the measured numerical value is not; the value depends on the experimental conditions. Therefore, to define the quantity of a catalyst in katals, the rate of conversion of a defined chemical reaction is specified as moles reacted per second. One katal of trypsin, for example, is that amount of trypsin which breaks one mole of peptide bonds in one second under specified conditions.

Definition

SI multiples

Origin

The name "katal" has been used for decades, and the unit became an official SI unit in 1999. The name comes from the Ancient Greek κατάλυσις, meaning "dissolution"; the word "catalysis" itself is a Latinized form of the Greek word.