Katal

Template:Short description Template:For Template:Cleanup Template:Infobox Unit The katal (symbol: kat) is a unit of the International System of Units (SI)<ref name=":1">Template:Cite journal</ref> used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts. One katal is that catalytic activity that will raise the rate of conversion by one mole per second in a specified assay system.<ref name=":1" />

The unit "katal" is not attached to a specified measurement procedure or assay condition, but any given catalytic activity is: the value measured depends on experimental conditions that must be specified.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref> Therefore, to define the quantity of a catalyst in katals, the catalysed rate of conversion (the rate of conversion in presence of the catalyst minus the rate of spontaneous conversion) of a defined chemical reaction is measured in moles per second.<ref>Template:Cite journal</ref> One katal of trypsin, for example, is that amount of trypsin which breaks one mole of peptide bonds in one second under the associated specified conditions.Template:Clarify

Definition

One katal refers to an amount of enzyme that gives a catalysed rate of conversion of one mole per second.<ref>Template:Cite journal</ref><ref name=":0">Template:Cite journal</ref> Because this is such a large unit for most enzymatic reactions, the nanokatal (nkat) is used in practice.<ref name=":0" />

<math alt="katal equals mole per second">\text{kat}=\frac{\text{mol}}{\text{s}}</math>

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.

History

The General Conference on Weights and Measures and other international organizations recommend use of the katal.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It replaces the non-SI enzyme unit of catalytic activity. The enzyme unit is still more commonly used than the katal,<ref name=":0" /> especially in biochemistry.Template:Citation needed<ref>Template:Cite journal</ref> The adoption of the katal has been slow.<ref name=":0" /><ref>Template:Cite journal</ref>

Origin

The name "katal" has been used for decades. The first proposal to make it an SI unit came in 1978,<ref name=":0" /><ref>Template:Cite journal</ref> and it became an official SI unit in 1999.<ref name=":0" /><ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The name comes from the Ancient Greek κατάλυσις (katalysis), meaning "dissolution";<ref name="AHD">Template:Citation</ref> the word "catalysis" itself is a Latinized form of the Greek word.<ref name="AHD"/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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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