A major phosphotyrosyl-protein phosphatase from bovine heart is associated with a low-molecular-weight acid phosphatase.
The phosphotyrosyl [Tyr(P)]-immunoglobulin G (IgG) phosphatase activity in the extracts of bovine heart, bovine brain, human kidney, and rabbit liver can be separated by DEAE-cellulose at neutral pH into two fractions. The unbound fraction exhibits a higher activity at acidic than neutral pH while the reverse is true for the bound fraction. Of all tissues examined, the Tyr(P)-IgG phosphatase activity in the unbound fraction measured at pH 5.0 is higher than that in the bound fraction measured at pH 7.2. The acid Tyr(P)-IgG phosphatase activity has been extensively purified from bovine heart. It copurified with an acid phosphatase activity (p-nitrophenyl phosphate (PNPP) as a substrate) throughout the purification procedure. These two activities coelute from various ion-exchange and gel filtration chromatographies and comigrate on polyacrylamide gel electrophoresis, indicating that they reside on the same protein molecule. The phosphatase has a Mr = 15,000 by gel filtration and exhibits an optimum between pH 5.0 and 6.0 when either Tyr(P)-IgG-casein or PNPP is the substrate. It is highly specific for Tyr(P)-protein with little activities toward phosphoseryl [Ser(P)]- or phosphothreonyl [Thr(P)]-protein. The enzyme activities toward Tyr(P)-casein and PNPP are strongly inhibited by microM molybdate and vanadate but insensitive to inhibition by L(+)-tartrate, NaF, or Zn2+. The molecular and catalytic properties of the acid Tyr(P)-protein phosphatase purified from bovine heart are very similar to those of the low-molecular-weight acid phosphatases of Mr = 14,000 previously identified and purified from the cytosolic fraction of human liver, placenta, and other animal tissues.
Chernoff
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D000135:Acid Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D002384:Catalysis; D002417:Cattle; D002848:Chromatography, DEAE-Cellulose; D006801:Humans; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases; D011817:Rabbits; D013379:Substrate Specificity
D010749:Phosphoprotein Phosphatases; D000135:Acid Phosphatase; D017027:Protein Tyrosine Phosphatases