Pseudophosphatases (obsolete)

Human pseudophosphatases

Second phosphatase domain (D2) in receptor PTPs

Most receptor PTPs have two tandem phosphatase domains. The 2nd phosphatase domain has no or negligible activity. The 2nd domain can interact with 1st domain in both intra- and intermolecular manners, therefore regulating RPTP stability, specificity, and dimerization [1, 2].

These phosphatases include:

• Subfamily PTPRA: PTPRA and PTPRE
• Subfamily PTPRC: PTPRC
• Subfamily PTPRD: PTPRD, PTPRF and PTPRS
• Subfamily PTPRG: PTPRG and PTPRZ1
• Subfamily PTPRK: PTPRK, PTPRM, PTPRT and PTPRU

Auxilin subfamily

There are two members of auxilin subfamily in human, GAK and DNAJC6. Both GAK and DNAJC6 phosphatase domains have been shown to bind phospholipids [3, 4]. The phosphatase domains of both are predicted to be inactive due to arginine in catalytic motif Cx5R is replaced by alanine.

Fold CC1

Family PTP

Subfamily PTPRC

Gene PTPRC (CD45)

Human has a single member of this subfamily, PTPRC (a.k.a. CDC45), a vertebrate-specific receptor PTP involved in immune signaling. It has two tandem phosphatase domain. The functional role of the D2 domain has not yet been defined although possible roles in regulating RPTP stability, specificity, and dimerization have been suggested [2].

Subfamily PTPRG

Gene PTPRG

Human has a single member of this subfamily, PTPRC (a.k.a. CDC45), a vertebrate-specific receptor PTP involved in immune signaling. It has two tandem phosphatase domain. The functional role of the D2 domain has not yet been defined although possible roles in regulating RPTP stability, specificity, and dimerization have been suggested [2].

Subfamily PTPRN

Human PTPRN (IA-2) and PTPRN2 have been proposed to be enzymatically inactive due to mutations at catalytic Cx5R motif and WPD motif [5]. However, PTPRN2 has been reported to be phosphatidylinositol phosphatase [6].

Subfamily PTPN23 (HD-PTP)

PTPN23 was reported to be catalytically inactive, - no phosphatase activity toward tyrosine or lipid. It was proposed that serine at position 1452 within Cx5R catalytic motif caused the inactivity. Replacing serine with alanine, which is found in catalytically active PTPs, can restore the phosphatase activity [7]. However, another study found SRC, E-cadherin, and beta-catenin are direct substrates of PTPN23 [8]. But, yet another study showed that PTPN23 did not modulate the levels of Src phosphorylation both in vitro and in vivo [9].

Family Myotubularin

Subfamily MTMR5 (SBF)

MTMR5 (SBF1) and MTMR13 (SBF2)

References

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