title: Identification of a non-purple tartrate-resistant acid phosphatase: an evolutionary link to Ser/Thr protein phosphatases?
abstract: BACKGROUND
  Tartrate-resistant acid phosphatases (TRAcPs), also known as purple acid phosphatases (PAPs), are a family of binuclear metallohydrolases that have been identified in plants, animals and fungi. The human enzyme is a major histochemical marker for the diagnosis of bone-related diseases. TRAcPs can occur as a small form possessing only the ~35 kDa catalytic domain, or a larger ~55 kDa form possessing both a catalytic domain and an additional N-terminal domain of unknown function. Due to its role in bone resorption the 35 kDa TRAcP has become a promising target for the development of anti-osteoporotic chemotherapeutics.
  
  
  RESULTS
  A new human gene product encoding a metallohydrolase distantly related to the ~55 kDa plant TRAcP was identified and characterised. The gene product is found in a number of animal species, and is present in all tissues sampled by the RIKEN mouse transcriptome project. Construction of a homology model illustrated that six of the seven metal-coordinating ligands in the active site are identical to that observed in the TRAcP family. However, the tyrosine ligand associated with the charge transfer transition and purple color of TRAcPs is replaced by a histidine.
  
  
  CONCLUSIONS
  The gene product identified here may represent an evolutionary link between TRAcPs and Ser/Thr protein phosphatases. Its biological function is currently unknown but is unlikely to be associated with bone metabolism.
authors.affiliation: School of Molecular and Microbial Sciences, The University of Queensland, St, Lucia, 4072, Australia. k.hadler@uq.edu.au
authors.forename: Kieran S
authors.initials: KS
authors.lastname: Hadler
authors.forename: Thomas
authors.initials: T
authors.lastname: Huber
authors.forename: A Ian
authors.initials: AI
authors.lastname: Cassady
authors.forename: Jane
authors.initials: J
authors.lastname: Weber
authors.forename: Jodie
authors.initials: J
authors.lastname: Robinson
authors.forename: Allan
authors.initials: A
authors.lastname: Burrows
authors.forename: Gregory
authors.initials: G
authors.lastname: Kelly
authors.forename: Luke W
authors.initials: LW
authors.lastname: Guddat
authors.forename: David A
authors.initials: DA
authors.lastname: Hume
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schenk
authors.forename: Jack U
authors.initials: JU
authors.lastname: Flanagan
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