Editing Urease (section)

==Structure==

A 1984 study focusing on urease from [[jack bean]] found that the [[active site]] contains a pair of [[nickel]] centers.<ref>{{cite journal | pmid = 6398286 | title=Nickel--an essential element | year=1984 | journal=IARC Sci. Publ. | pages=339–65 | vauthors=Anke M, Groppel B, Kronemann H, Grün M | issue=53}}</ref> [[In vitro]] activation also has been achieved with [[manganese]] and [[cobalt]] in place of nickel.<ref name="pmid20046957">{{cite journal | vauthors = Carter EL, Flugga N, Boer JL, Mulrooney SB, Hausinger RP | title = Interplay of metal ions and urease | journal = Metallomics | volume = 1 | issue = 3 | pages = 207–21 | date = 1 January 2009 | pmid = 20046957 | pmc = 2745169 | doi = 10.1039/b903311d }}</ref>  Lead salts are [[Enzyme inhibitor|inhibiting]].

The [[molecular weight]] is either 480 [[Atomic mass unit|kDa]] or 545 [[Atomic mass unit|kDa]] for jack-bean urease (calculated mass from the amino acid sequence). 840 amino acids per molecule, of which 90 are cysteine residues.<ref name="Molecular Catalysis B 2009">{{cite journal| vauthors = Krajewska B |title=Ureases I. Functional, catalytic and kinetic properties: A review|journal=Journal of Molecular Catalysis B: Enzymatic|date=30 June 2009|volume=59|issue=1–3|pages=9–21|doi=10.1016/j.molcatb.2009.01.003}}</ref>

The optimum [[pH]] is 7.4 and optimum temperature is 60&nbsp;°C.  Substrates include urea and [[hydroxyurea]].

Bacterial ureases are composed of three distinct subunits, one large catalytic (α 60–76kDa) and two small (β 8–21 kDa, γ 6–14 kDa) commonly forming (αβγ)<sub>3</sub> trimers [[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), they are cysteine-rich enzymes, resulting in the enzyme molar masses between 190 and 300kDa.<ref name="Molecular Catalysis B 2009"/>

An exceptional urease is obtained from ''Helicobacter'' sp..  These are composed of two subunits, α(26–31 kDa)-β(61–66 kDa).  These subunits form a supramolecular (αβ)<sub>12</sub> [[dodecameric]] complex.<ref name="pmid11373617">{{cite journal | vauthors = Ha NC, Oh ST, Sung JY, Cha KA, Lee MH, Oh BH | title = Supramolecular assembly and acid resistance of Helicobacter pylori urease | journal = Nature Structural Biology | volume = 8 | issue = 6 | pages = 505–509 | date = 31 May 2001 | pmid = 11373617 | doi = 10.1038/88563 | s2cid = 26548257 }}</ref> of repeating α-β subunits, each coupled pair of subunits has an active site, for a total of 12 active sites.<ref name="pmid11373617" /> It plays an essential function for survival, neutralizing [[gastric acid]] by allowing [[urea]] to enter into [[periplasm]] via a [[proton-gated urea channel]].<ref name="pmid23222544">{{cite journal | vauthors = Strugatsky D, McNulty R, Munson K, Chen CK, Soltis SM, Sachs G, Luecke H | title = Structure of the proton-gated urea channel from the gastric pathogen Helicobacter pylori | journal = Nature | volume = 493 | issue = 7431 | pages = 255–258 | date = 8 December 2012 | pmid = 23222544 | doi = 10.1038/nature11684 | pmc=3974264}}</ref> The presence of urease is used in the diagnosis of ''[[Helicobacter]]'' species.

All bacterial ureases are solely cytoplasmic, except for those in ''Helicobacter pylori'', which along with its cytoplasmic activity, has external activity with host cells. In contrast, all plant ureases are cytoplasmic.<ref name="Molecular Catalysis B 2009"/>

Fungal and plant ureases are made up of identical subunits (~90 kDa each), most commonly assembled as trimers and hexamers. For example, jack bean urease has two structural and one catalytic subunit. The α subunit contains the active site, it is composed of 840 amino acids per molecule (90 cysteines), its molecular mass without Ni(II) ions amounting to 90.77 kDa. The mass of the [[hexamer]] with the 12 nickel ions is 545.34 kDa. Other examples of homohexameric structures of plant ureases are those of soybean, pigeon pea and cotton seeds enzymes.<ref name="Molecular Catalysis B 2009"/>

It is important to note, that although composed of different types of subunits, ureases from different sources extending from bacteria to plants and fungi exhibit high homology of amino acid sequences. The single plant urease chain is equivalent to a fused γ-β-α organization. The ''Helicobacter'' "α" is equivalent to a fusion of the normal bacterial γ-β subunits, while its "β" subunit is equivalent to the normal bacterial α.<ref name="Molecular Catalysis B 2009"/> The three-chain organization is likely ancestral.<ref name="pmid30094078">{{cite journal |last1=Kappaun |first1=K |last2=Piovesan |first2=AR |last3=Carlini |first3=CR |last4=Ligabue-Braun |first4=R |title=Ureases: Historical aspects, catalytic, and non-catalytic properties - A review. |journal=Journal of Advanced Research |date=September 2018 |volume=13 |pages=3–17 |doi=10.1016/j.jare.2018.05.010 |pmid=30094078 |pmc=6077230 |doi-access=free}}</ref>