Phosphoprotein phosphatase activity of human prostate acid phosphatase.
Human prostate acid phosphatase (EC 3.1.3.2) has been shown to dephosphorylate different phosphoproteins with the maximum rate at pH 4.0-4.5. The activity with phosvitin is distinctly higher than with beta-casein, casein and most of all than with riboflavin-binding protein. The native phosvitin is homogeneous on isoelectric focusing with pI value of 2.1, whereas phosvitin partially dephosphorylated (in about 15%) by the prostate acid phosphatase shows multiple bands with pI values of 3.5 - 6.8 or higher. The phosphate groups bound to serine residues are removed enzymatically twice as fast as phosphothreonine residues. The apparent Km value for phosvitin was 2.4 X 10(-7) M, and is by three orders of magnitude lower than Km of p-nitrophenyl phosphate (2.9 X 10(-4) M). The competitive inhibitors of prostate acid phosphatase, fluoride and L(+)-tartrate, show the same Ki values for phosvitin and p-nitrophenyl phosphate.
D000135:Acid Phosphatase / Q000378:metabolism*; D004590:Electrophoresis, Paper; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D007700:Kinetics; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D011467:Prostate / Q000201:enzymology*; D013379:Substrate Specificity
D010769:Phosphothreonine; D010768:Phosphoserine; D010749:Phosphoprotein Phosphatases; D000135:Acid Phosphatase