Katal
Encyclopedia
The katal is the SI
unit of catalytic
activity. It is a derived SI
unit for expressing quantity values of catalytic activity of enzyme
s 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 units of concentration per second (or moles per liter 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.
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
unit of catalytic
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
activity. It is a derived SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
unit for expressing quantity values of catalytic activity of enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s and other catalysts. Its use is recommended by the General Conference on Weights and Measures
General Conference on Weights and Measures
The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures . It is one of the three organizations established to maintain the International System of Units under the terms of the Convention du Mètre of 1875...
and other international organizations. It replaces the non-SI enzyme unit
Enzyme unit
The enzyme unit is a unit for the amount of a particular enzyme.One U is defined as the amount of the enzyme that catalyzes the conversion of 1 micro mole of substrate per minute...
. Enzyme units are, however, still more commonly used than the katal in practice at present, especially in biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
.
The katal is not used to express the rate of a reaction; that is expressed in units of concentration per second (or moles per liter 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
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
, for example, is that amount of trypsin which breaks a mole
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
of peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
bonds per second under specified conditions.
External links
- Unit "katal" for catalytic activity (IUPAC Technical Report) Pure Appl. Chem. Vol. 73, No. 6, pp. 927–931 (2001) http://www.iupac.org/publications/pac/2001/7306/7306x0927.html