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From Wikipedia, the free encyclopedia

The katal (symbol: kat) is the SI unit of catalytic activity.[1] It is a derived SI unit for expressing quantity values of catalytic activity of enzymes and other catalysts. Its use is recommended by the General Conference on Weights and Measures and other international organizations. It replaces the non-SI enzyme unit. Enzyme units are, however, still more commonly used than the katal in practice at present, especially in biochemistry.

The katal is not used to express the rate of a reaction; that is expressed in moles per second. Rather, it is used to express catalytic activity which is a property of the catalyst. The katal is invariant of the measurement procedure, but the numerical quantity value is not and depends on the experimental conditions. Therefore, in order to define the quantity of a catalyst, the rate of conversion of a defined chemical reaction has to be specified, preferably of the first order, under strictly controlled conditions. One katal of trypsin, for example, is that amount of trypsin which breaks a mole of peptide bonds per second under specified conditions.



1 kat = 1 mol/s

SI multiples

SI multiples for katal (kat)
Submultiples Multiples
Value Symbol Name Value Symbol Name
10–1 kat dkat decikatal 101 kat dakat decakatal
10–2 kat ckat centikatal 102 kat hkat hectokatal
10–3 kat mkat millikatal 103 kat kkat kilokatal
10–6 kat µkat microkatal 106 kat Mkat megakatal
10–9 kat nkat nanokatal 109 kat Gkat gigakatal
10–12 kat pkat picokatal 1012 kat Tkat terakatal
10–15 kat fkat femtokatal 1015 kat Pkat petakatal
10–18 kat akat attokatal 1018 kat Ekat exakatal
10–21 kat zkat zeptokatal 1021 kat Zkat zettakatal
10–24 kat ykat yoctokatal 1024 kat Ykat yottakatal


The name katal has been used for decades and it became an official SI unit in 1999.


  1. ^ Nomenclature Committee of the International Union of Biochemistry (NC-IUB) (1979). "Units of Enzyme Activity". Eur. J. Biochem. 97: 319–20. doi:10.1111/j.1432-1033.1979.tb13116.x.  

External links

  • Unit "katal" for catalytic activity (IUPAC Technical Report) Pure Appl. Chem. Vol. 73, No. 6, pp. 927-931 (2001) [1]

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