Enzyme unit

The enzyme unit (U) is an ancient unit indicating the enzyme activity. It was partially replaced by the Katal; when using the Katal however, change the number values ​​. Therefore U is used in medicine and clinical chemistry further.

One enzyme unit U corresponding to the amount of enzyme that catalyzes the conversion of one micromol of substrate per minute under defined conditions. The conditions (temperature, substrate concentration, pH, etc.) should be selected so that a maximum rate of reaction is achieved. This makes corresponding additional information needed and complicates the comparability of information. Frequently, therefore, a uniform temperature of 30 ° C is based on at least.

Commercially available enzymes for molecular genetics are often sold graded according to enzyme units. For restriction endonucleases but they are defined by the complete digestion of 1 ug of genomic DNA from the λ phage in one hour, under certain reaction conditions in the rule. Λ DNA is not cut, based on the definition of any other DNA, such as the adenovirus-2 genome.

In Germany, the 2009 Katal is legal unit of measurement since October 3.