Protein kinase activities in human prostatic secretion: biochemical characterization and effect of prostatitis

The enzymic properties of two protein phosphokinase activities in human prostatic secretion were determined with partially dephosphorylated phosvitin and lysine-rich histones as acceptor protein substrates. Both kinase activities had pH optima of 8.0 and required Mg2+. The histone kinase activity was stimulated by dithiothreitol and inhibited by increased ionic strength. Similarly, it was inhibited by the cAMP-dependent protein kinase inhibitor. MnCl2 and CaCl2 substituted poorly for MgCl2. In contrast, the phosvitin kinase activity was stimulated by increased ionic strength and inhibited by dithiothreitol. It was, however, unaffected by the cAMP-dependent protein kinase inhibitor. MnCl2 and CaCl2 substituted effectively for MgCl2. Both kinase activities were reduced 60% to 65% in prostatic fluids in men with chronic prostatitis.