Urease (from the Greek. Ούρον - urine and -ase - the standard affix of the biochemical nomenclature, indicating the substance belongs to the class of enzymes) is a hydrolytic enzyme from the amidase group, which has the specific property of catalyzing the hydrolysis of urea to carbon dioxide and ammonia :
CO (NH 2 ) 2 + H 2 O → CO 2 + 2NH 3
Urease is found in bacteria (for example, in urobacteria ), yeast , plants (especially a lot of it is found in soybean seeds ), as well as in a number of invertebrates ; in animal cells, in which urea is formed as the main product of nitrogen metabolism, urease is absent. In humans and animals, urease is formed by the bacterial flora. In 1926, the American biochemist James Sumner proved that urease is a protein .
Features
- Molecular mass : 480 000 a. eat.
- Optimum pH (pH): 7.4
- Optimum temperature: 60 ° C
- Inhibitors: heavy metals (Pb 2+ ), hydrogen peroxide , acetohydroxamic acid. Reactivation of urease inhibited by heavy metals is possible by reaction with ethylenediaminetetraacetic acid .
- Enzymatic specifics: urea and hydroxyurea .
Urease consists of two subunits (α and β) connected to dimers , which, in turn, are connected to each other in trimers (αβ) 3. Trimers form a special complex structure ((ab) 3) 4. An unusual urease was found in Helicobacter pylori , in which 4 out of 6 ordinary enzyme subunits combined a common complex of 24 subunits (α12β12). It is believed that this supramolecular complex provides additional stability of the enzyme in this bacterium, which produces ammonia in order to neutralize the hydrochloric acid of the gastric juice. The presence of a high activity of urease is used as a diagnostic sign of the bacteria Helicobacter and Ureaplasma urealyticum .
Diagnostic Use
Some pathogens of the gastrointestinal tract and urinary tract produce urease, which allows the use of the urease test (in conjunction with other criteria) to identify them, and under certain circumstances for semi-quantitative determination. Known laboratory methods for determining the content of urea in urine, based on its hydrolysis in the presence of soy urease, followed by measuring the amount of ammonia released as a result of the reaction.
Other Uses
Urease-based biosensors for the detection of heavy metals were used to quantify the total water pollution by heavy metal ions.