Urease: Difference between revisions
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<StructureSection load='4ac7' size=' | <StructureSection load='4ac7' size='350' side='right' scene='' caption='Urease α (pink), β (green), γ (grey) chains complex with citrate, sulfate and Ni+2 ions (green) (PDB code [[4ac7]])'> | ||
=Introduction= | =Introduction= | ||
'''Urease''' is a nickel-dependent metalloenzyme, is synthesized by plants, some bacteria, and fungi <ref name="urease">PMID: PMC2443974 </ref>. | '''Urease''' is a nickel-dependent metalloenzyme, is synthesized by plants, some bacteria, and fungi <ref name="urease">PMID: PMC2443974 </ref>. | ||
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Ureases are among the few enzymes that require nickel for activity. It is known that binding of nickel to urease is very specific and tight and the removal of metal ions can be achieved only by harsh treatment with denaturants or acids,<ref name="nickel">Dixon, N. E., Riddles, P. W., Gazzola, C., Blakeley, R. L. & Zerner, B. (1980). Jack been urease (EC 3.5.1.5). II. The relationship between nickel, enzymatic activity, and the “abnormal” ultraviolet spectrum. The nickel content of jack beans. Can. J. Biochem. 58, 474–480. </ref> which is not the case in most other metalloenzymes. In vivo incorporation of nickel in both bacterial and plant ureases requires a set of accessory proteins that appear to act as urease-specific chaperones <ref name="nickel2">Moncrief, M. C. & Hausinger, R. P. (1996). Nickel incorporation into urease. In Mechanisms of Metallo- center Assembly (Hausinger, R. P., Eichhorn, G. L. & Marzilli, L. G., eds), pp. 151–171, Elsevier Press, New York, NY. </ref>. | Ureases are among the few enzymes that require nickel for activity. It is known that binding of nickel to urease is very specific and tight and the removal of metal ions can be achieved only by harsh treatment with denaturants or acids,<ref name="nickel">Dixon, N. E., Riddles, P. W., Gazzola, C., Blakeley, R. L. & Zerner, B. (1980). Jack been urease (EC 3.5.1.5). II. The relationship between nickel, enzymatic activity, and the “abnormal” ultraviolet spectrum. The nickel content of jack beans. Can. J. Biochem. 58, 474–480. </ref> which is not the case in most other metalloenzymes. In vivo incorporation of nickel in both bacterial and plant ureases requires a set of accessory proteins that appear to act as urease-specific chaperones <ref name="nickel2">Moncrief, M. C. & Hausinger, R. P. (1996). Nickel incorporation into urease. In Mechanisms of Metallo- center Assembly (Hausinger, R. P., Eichhorn, G. L. & Marzilli, L. G., eds), pp. 151–171, Elsevier Press, New York, NY. </ref>. | ||
One of the most common bacterial urease is the ''Helicobacter pylori'' since it has been implicated in peptic ulcers and stomach cancer <ref name="pylori">Covacci, A., Telford, J. L., Del Giudice, G., Parsonnet, J. & Rappuoli, R. (1999). Helicobacter pylori virulence and genetic geography. Science, 284, 1328–1333.</ref>. In plants, urease is widely distributed in leguminous seeds and is suggested to play an important role in seed germination<ref name="pylori">Covacci, A., Telford, J. L., Del Giudice, G., Parsonnet, J. & Rappuoli, R. (1999). Helicobacter pylori virulence and genetic geography. Science, 284, 1328–1333.</ref>. Plant ureases are also suggested to participate in seed chemical defenses <ref name="def">Polacco, J. C. & Holland, M. A. (1993). Roles of urease in plant cells. Int. Rev. Cytol. 145, 65–103.</ref>. | One of the most common bacterial urease is the ''Helicobacter pylori'' since it has been implicated in peptic ulcers and stomach cancer <ref name="pylori">Covacci, A., Telford, J. L., Del Giudice, G., Parsonnet, J. & Rappuoli, R. (1999). Helicobacter pylori virulence and genetic geography. Science, 284, 1328–1333.</ref>. In plants, urease is widely distributed in leguminous seeds and is suggested to play an important role in seed germination<ref name="pylori">Covacci, A., Telford, J. L., Del Giudice, G., Parsonnet, J. & Rappuoli, R. (1999). Helicobacter pylori virulence and genetic geography. Science, 284, 1328–1333.</ref>. Plant ureases are also suggested to participate in seed chemical defenses <ref name="def">Polacco, J. C. & Holland, M. A. (1993). Roles of urease in plant cells. Int. Rev. Cytol. 145, 65–103.</ref>. | ||
See also [[Urease (Hebrew)]]. | |||
=Reaction= | =Reaction= | ||
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[[Urease]] ('''Urea Amidohydrolase''' [[EC]] [[Hydrolases|3.5.1.5]]) catalyzes the hydrolysis of urea to ammonia and carbon dioxide, thus allowing organisms to use exogenous and internally generated urea as a nitrogen source<ref name="urease">PMID: PMC2443974 </ref>. | [[Urease]] ('''Urea Amidohydrolase''' [[EC]] [[Hydrolases|3.5.1.5]]) catalyzes the hydrolysis of urea to ammonia and carbon dioxide, thus allowing organisms to use exogenous and internally generated urea as a nitrogen source<ref name="urease">PMID: PMC2443974 </ref>. | ||
The multi-subunit enzyme usually has a 3:3 (alpha:beta) stoichiometry with a 2-fold symmetric structure (note that the image above gives the structure of the asymmetric unit, one-third of the true biological assembly). An exceptional urease is found in ''Helicobacter pylori'', which combines four of the regular six-subunit enzymes in an overall tetrahedral assembly of 24 subunits (α12β12). This supra-molecular assembly is thought to confer additional stability for the enzyme in this organism, which functions to produce ammonia in order to neutralise gastric acid. The presence of urease is used in | The multi-subunit enzyme usually has a 3:3 (alpha:beta) stoichiometry with a 2-fold symmetric structure (note that the image above gives the structure of the asymmetric unit, one-third of the true biological assembly). An exceptional urease is found in ''Helicobacter pylori'', which combines four of the regular six-subunit enzymes in an overall tetrahedral assembly of 24 subunits (α12β12). This supra-molecular assembly is thought to confer additional stability for the enzyme in this organism, which functions to produce ammonia in order to neutralise gastric acid. The presence of urease is used in t''Update February 2013''he diagnosis of Helicobacter species<ref name="characteristics">http://en.wikipedia.org/wiki/Urease </ref>. | ||
Molecular weight: 480 kDa or 545 kDa for Jack Bean Urease | Molecular weight: 480 kDa or 545 kDa for Jack Bean Urease | ||
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{{Clear}} | {{Clear}} | ||
The present study consistently supports an interaction of fluoride with the nickel centres in the urease active site in which <scene name='59/596313/Cv/17'>one fluoride competitively binds</scene> (<span style="color:salmon;background-color:black;font-weight:bold;">colored in salmon</span>) to the Ni(II) ion proposed to coordinate urea in the initial step of the catalytic mechanism, while <scene name='59/596313/Cv/18'>another fluoride uncompetitively substitutes</scene> (<span style="color:cyan;background-color:black;font-weight:bold;">colored in cyan</span>) the Ni(II)-bridging hydroxide, blocking its nucleophilic attack on urea. | The present study consistently supports an interaction of fluoride with the nickel centres in the urease active site in which <scene name='59/596313/Cv/17'>one fluoride competitively binds</scene> (<span style="color:salmon;background-color:black;font-weight:bold;">colored in salmon</span>) to the Ni(II) ion proposed to coordinate urea in the initial step of the catalytic mechanism, while <scene name='59/596313/Cv/18'>another fluoride uncompetitively substitutes</scene> (<span style="color:cyan;background-color:black;font-weight:bold;">colored in cyan</span>) the Ni(II)-bridging hydroxide, blocking its nucleophilic attack on urea. | ||
=3D structures of urease= | |||
[[Urease 3D structures]] | |||
</StructureSection> | </StructureSection> | ||
__NOTOC__ | __NOTOC__ | ||
=Additional Resources= | =Additional Resources= | ||
For additional information on Urinary Tract Infection, See: [[1tr7]] <br /> | For additional information on Urinary Tract Infection, See: [[1tr7]] <br /> | ||
