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Unit systemSI derived unit
Unit ofcatalysis
In SI base units:mol/s

The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (SI).[1] It is a derived SI unit for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts.

The General Conference on Weights and Measures and other international organizations recommend use of the katal.[2] It replaces the non-SI enzyme unit of catalytic activity. Enzyme units are, however, still more commonly used than the katal, especially in biochemistry.[citation needed]

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.[citation needed] 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.[citation needed] One katal of trypsin, for example, is that amount of trypsin which breaks one mole of peptide bonds in one second under specified conditions.


SI multiples[edit]

SI multiples of katal (kat)
Submultiples Multiples
Value SI symbol Name Value SI 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 the unit became an official SI unit in 1999. The name comes from the Ancient Greek κατάλυσις (katalysis), meaning "dissolution",[3]; the word "catalysis" itself is a Latinized form of the Greek word.[3][4]


  1. ^ Nomenclature Committee of the International Union of Biochemistry (NC-IUB) (1979). "Units of Enzyme Activity". Eur. J. Biochem. 97 (2): 319–20. doi:10.1111/j.1432-1033.1979.tb13116.x.
  2. ^ "SI Brochure, Table 3: Coherent derived units in the SI with special names and symbols)". Bureau international des poids et mesures (BIPM). Retrieved 2019-05-13.
  3. ^ a b Houghton Mifflin Harcourt, The American Heritage Dictionary of the English Language, Houghton Mifflin Harcourt
  4. ^ Harper, Douglas. "catalysis (n.)". Etymonline. Retrieved 2019-04-03.

External links[edit]