GLYCOPROTEIN EXHIBITING IMMUNOLOGICAL AND ENZYMATIC-ACTIVITIES OF HUMAN PROSTATIC ACID-PHOSPHATASE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (8) , 3841-3846
Abstract
A glycoprotein (GP) which is immunochemically and biologically related to human prostatic acid phosphatase (PA) was isolated from human seminal plasma by ammonium sulfate precipitation followed by sequential concanavalin A:Sepharose 4B column, anion-exchange chromatography and gel filtration. The purified GP was shown to be homogeneous by disc- and sodium dodecyl sulfate: polyacrylamide gel electrophoresis [SDS-PAGE]. The apparent MW of purified GP was estimated to be 50,00 by gel filtration and 45,000 by SDS-PAGE. In gel diffusion against antiserum to purified PAP, a partial immunological identity was shown between GP and PAP. This was further confirmed by an inhibition reaction between GP and antiserum to purified GP by PAP. Significantly, 30% of PAP enzyme activity was inhibited by anti-GP antiserum, while only 5% was inhibited by anti-PAP antiserum. Purified GP exhibited a weak, but significant, acid phosphatase activity by hydrolyzing .alpha.-naphthyl phosphate at pH 5.6. The Km and Vmax for GP are 1.6 .times. 10-4 M and 0.056 .mu.mol/min per .mu.g protein, respectively, using .alpha.-naphthyl phosphate as the substrate. In the presence of anti-PAP antibody, the enzyme activity of GP was enhanced several-fold. Furthermore, the acid phosphatase activity of GP also was inhibited by tartrate, which is the most commonly used inhibitor for PAP. GP and PAP have different carbohydrate content, amino acid composition, amino-terminal sequence, and peptide map. Thus, GP represents a newly identified protein. The significance of these results at molecular and clinical levels is discussed. The association of acid phosphatase activity with prostate cancer is discussed.