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Endogenous protein substrates for prostatic acid phosphatase in human prostate
Author(s) -
Lee Hansoo,
Ming Chu T.,
Lee ChingLi
Publication year - 1991
Publication title -
the prostate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.295
H-Index - 123
eISSN - 1097-0045
pISSN - 0270-4137
DOI - 10.1002/pros.2990190306
Subject(s) - phosphoprotein , dephosphorylation , phosphoserine , prostatic acid phosphatase , biochemistry , phosphatase , phosphorylation , serine , dusp6 , protein tyrosine phosphatase , threonine , tyrosine , biology , endogeny , kinase , chemistry , protein phosphatase 2 , acid phosphatase , enzyme
In order to identify the endogenous phosphoprotein substrates for human prostatic acid phosphatase (PAP), cellular proteins of human normal, benign, and malignant prostatic tissues as well as carcinoma cell lines were phosphorylated by the cellular kinases in the presence of (γ‐ 32 P)‐ATP and then were subjected to dephosphorylation reaction by PAP. Of several endogenous phosphoproteins, PAP preferentially dephosphorylated a cytosolic protein of Mr 83 kDa. The dephosphorylation of the 83 kDa phosphoprotein (designated pp83) by PAP was uniformly observed in all cells/tissues of prostate origin, and was completely inhibited by L(+)‐tartrate, the classic inhibitor of PAP. Phosphoamino acid analysis revealed that pp83 was a tyrosine‐poor phosphoprotein and was mostly dephosphorylated by PAP at serine/threonine residues rather than tyrosine residues. Further comparison of dephosphorylation rate with that of an endogenous phosphotyrosine‐containing phosphoprotein (pp53) revealed that PAP possessed both phosphoserine/threonine protein phosphatase and phosphotyrosine protein phosphatase activity. These results demonstrate that pp83 apparently is an endogenous substrate of PAP in human prostate, and that, instead of a phosphotyrosine protein specific phosphatase, PAP is a universal protein phosphatase hydrolyzing equally well the phosphotyrosine, serine, and threonine residues.