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{{enzyme
| Name = xanthine phosphoribosyltransferase
| EC_number = 2.4.2.22
| CAS_number = 9023-10-3
| IUBMB_EC_number = 2/4/2/22
| GO_code = 0000310
| image = 
| width = 
| caption = 
}}
In [[enzymology]], a '''xanthine phosphoribosyltransferase''' ({{EC number|2.4.2.22}}) is an [[enzyme]] that [[catalysis|catalyzes]] the [[chemical reaction]]

:XMP + diphosphate <math>\rightleftharpoons</math> 5-phospho-alpha-D-ribose 1-diphosphate + xanthine

Thus, the two [[substrate (biochemistry)|substrates]] of this enzyme are [[XMP]] and [[diphosphate]], whereas its two [[product (chemistry)|products]] are [[5-phospho-alpha-D-ribose 1-diphosphate]] and [[xanthine]].

This enzyme belongs to the family of [[glycosyltransferase]]s, specifically the pentosyltransferases.  The systematic name of this enzyme class is '''XMP:diphosphate 5-phospho-alpha-D-ribosyltransferase'''. Other names in common use include '''Xan phosphoribosyltransferase''', '''xanthosine 5'-phosphate pyrophosphorylase''', '''xanthylate pyrophosphorylase''', '''xanthylic pyrophosphorylase''', '''XMP pyrophosphorylase''', '''5-phospho-alpha-D-ribose-1-diphosphate:xanthine''', '''phospho-D-ribosyltransferase''', '''9-(5-phospho-beta-D-ribosyl)xanthine:diphosphate''', and '''5-phospho-alpha-D-ribosyltransferase'''.  This enzyme participates in [[purine metabolism]].  

==Structural studies==

As of late 2007, 6 [[tertiary structure|structures]] have been solved for this class of enzymes, with [[Protein Data Bank|PDB]] accession codes {{PDB link|1A95}}, {{PDB link|1A96}}, {{PDB link|1A97}}, {{PDB link|1A98}}, {{PDB link|1NUL}}, and {{PDB link|2FXV}}.

==References==
{{reflist|1}}
* {{cite journal | author = Krenitsky TA, Neil SM, Miller RL | date = 1970 | title = Guanine and xanthine phosphoribosyltransfer activities of Lactobacillus casei and Escherichia coli. Their relationship to hypoxanthine and adenine phosphoribosyltransfer activities | journal = J. Biol. Chem.  | volume = 245 | pages = 2605&ndash;11  | pmid = 4910918 | issue = 10 }}

{{enzyme-stub}}

[[Category:EC 2.4.2]]
[[Category:Enzymes of known structure]]