from Wikipedia, the free encyclopedia
Physical unit
Unit name Catal
Unit symbol
Physical quantity (s) catalytic activity
Formula symbol
system International system of units
In SI units
Derived from Mol , second

The katal ( kat ) is a special name for the SI unit of the catalytic activity and thus the enzyme activity .

A katal means one mole of substrate turnover per second and can be converted into the previously used enzyme unit  (U) as follows :

In Germany, the katal has been the legal unit in metrology since October 3, 2009 .

In clinical chemistry , catalytic activities per volume are measured under standard conditions and then serve as a measure of the enzyme concentration. The unit (i.e. enzyme unit per liter) is still used for this use  .


The name Katal was proposed in 1972 by the enzyme commission of the IUB ( International Union of Biochemistry ) as the SI unit of measurement for enzyme activity. It was included in the catalog of derived SI units in 1999.


Individual evidence

  1. to note: the katal indicates the amount of enzyme as a catalyst, but not the amount of substrate; a katal means: enough enzyme that one mole of substrate per second can be converted with it as a catalyst ; the amount of substance of the enzyme can differ considerably from 1 mol: x mol of enzyme for 1 mol of substrate corresponds to 1 cat.
  2. Third ordinance amending the Units Ordinance of September 25, 2009 ( Federal Law Gazette I p. 3169 ).
  3. ^ Resolution 12 of the 21st meeting of the CGPM (1999) ( online , accessed September 13, 2019).