Acidic-phosphoprotein phosphatase activity of rat ventral prostate nuclei: apparent lack of effect of androgens.
A protein phosphatase activity has been demonstrated in nuclei of rat ventral prostate utilizing 32P-labelled phosvitin as a model acidic phosphoprotein substrate. This phosphoprotein phosphatase has a pH optimum of 6.7, is unaffected by the sulphydryl protecting agent 2-mercaptoethanol, and requires a divalent cation for maximal activity. Of the various divalent cations tested, Mg2+ is the most effective in reactivating the EDTA-inhibited enzyme. The phosphatase is inhibited by sodium flouride, sodium oxalate, N-ethylmaleimide, ATP and ADP but is relatively insensitive to ammonium molybdate. Increased ionic strength of the reaction medium also causes a reduction in the enzyme activity, e.g., by 48% at 200 mM sodium chloride. The activity of the acidic phosphoprotein phosphatase did not change significantly at 48 h or 96 h post-orchiectomy when expressed per unit of nuclear protein. However, it is reduced by approx. 30% at these times after castration if based on DNA content. The decline in activity per nucleus reflects the decrease in the realtive nuclear protein content observed at 48 h or 96 h post-orchiectomy. This suggests that the decline in the phosphorylation of prostatic nuclear acidic proteins which occurs upon androgen withdrawal is not due to increased nuclear phosphatase activity.
D000728:Androgens / Q000494:pharmacology* / Q000502:physiology; D000818:Animals; D002369:Castration; D002467:Cell Nucleus / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009698:Nucleoproteins / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010774:Phosvitin / Q000378:metabolism; D011467:Prostate / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D013737:Testis / Q000502:physiology
D000728:Androgens; D009698:Nucleoproteins; D010774:Phosvitin; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D008274:Magnesium