Katal

For the village in Iran, see Katal, Iran.

Katal
Unit system	SI derived unit
Unit of	catalysis
Symbol	kat
In SI base units:	mol/s

The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (SI). 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 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

One katal refers to an enzyme catalysing the reaction of one mole of substrate per second. Because this is such a large unit for most enzymatic reactions, the nanokatal (nkat) is used in practice.

${\text{kat}}={\frac {\text{mol}}{\text{s}}}$

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.

SI multiples

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
10−27 kat	rkat	rontokatal	1027 kat	Rkat	ronnakatal
10−30 kat	qkat	quectokatal	1030 kat	Qkat	quettakatal

History

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 adoption of the katal has been slow.

Origin

The name "katal" has been used for decades. The first proposal to make it an SI unit came in 1978, and it became an official SI unit in 1999. The name comes from the Ancient Greek κατάλυσις (katalysis), meaning "dissolution"; the word "catalysis" itself is a Latinized form of the Greek word.

External links

• Unit "katal" for catalytic activity (IUPAC Technical Report) Pure Appl. Chem. Vol. 73, No. 6, pp. 927–931 (2001) [1]
• René Dybkær (1 March 2002). "The Tortuous Road to the Adoption of katal for the Expression of Catalytic Activity by the General Conference on Weights and Measures". Clinical Chemistry. 48 (3): 586–590. doi:10.1093/clinchem/48.3.586. PMID 11861460. Archived from the original on 6 October 2008. Retrieved 8 December 2005.