Phosphatase Subfamily PPPRK TN

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Phosphatase Classification: Fold CC1:Superfamily CC1: Family PTP: Subfamily PTPRK (R2B): Technical notes

PTPRK has four members in human, with orthologs across the vertebrates. PTPRK is also found in invertebrate chordates

  • Ciona intestinalis (XP_002125715.3) has a full length prediction with the typical MAM-Ig-Fn3-Fn3-Fn3 -PTP-PTP architecture
  • Oikopleura dioca (CBY08646.1) has a MAM-Ig-FN3(2)-PTP(3) architecture, with one more PTP domain than typical.

Putative homologs of PTPRK are present in other invertebrates, but they have different domain architectures and their orthology to PTPRK is uncertain. These include:

  • PTP36E is similar to PTPRK but most or all members have lost their extracellular regions.
  • SpurPTP-sf4 and NvecPTP-sf2 are species-specific subfamilies that show some selectively similarity to PTPRK, but the orthology confidence is quite low.


This putative new subfamily is found in molluscs, and has a extracellular region with a Kringle domain, a CS-rich domain and some have a SKG6 transmembrane domain. Members include:

  • KRCS-Acal (XP_012937090.1) from Aplysia californica
  • KRCS_Bgla: with a KR-EGF_Lam-SKG6-PTP(2) architecture from Biomphalaria glabrata.
  • KRCS_Cgig (EKC20265.1) from Crassostrea gigas


This family has an N-terminal Kringle domain, followed by 3-4 FN3 domains, and twin intracellular PTP domains that look most like PTPRK. It is found in Lophotrochozoa including annelids and molluscs

  • Octopus bimaculoides (XP_014783726.1) KR-FN3(4)-PTP(2)
  • Crassostrea gigas (EKC35846.1): KR-FN3(3)-PTP(2)
  • Lingula anatina (XP_013393761.1): KR-Ig-FN3(3)-PTP(2)
  • Capitella teleta (ELU04626.1): Fragment: PTP(2)
  • Aplysia californica (XP_012937090.1): KR-SKG6-PTP(2)
  • Biomphalaria glabrata (XP_013067253.1) frag fn3(3)-PTP(2)

Other related subfamilies

PTPRK is similar to the SpurPTP-sf4 subfamily seen in sea urchin and the NvecPTP-sf2 subfamily seen in Nematostella, but most of these genes are fragments and their orthology is not clear, leading to their classification in separate subfamilies.