A polyamine-dependent protein kinase from bovine epididymal spermatozoa.

This study provides evidence for the occurrence of a biochemical function for the polyamines, spermidine and spermine, in bovine epididymal spermatozoa. Methods are described for the detection and isolation of a protein kinase from spermatozoa which catalyzed transfer of phosphate from [gamma-32P]ATP to a unique endogenous protein of Mr = 70,000 in a reaction that was polyamine-dependent. Enzymatic phosphorylation of the 70,000-dalton protein by the purified protein kinase was sharply activated, at times more than 80-fold, by the polyamines, spermidine and spermine. Spermidine and spermine, together in equimolar combination, synergistically activated the protein kinase when compared with all other possible combinations of putrescine, spermidine, or spermine. The polyamine-dependent protein kinase was resolved by phosphocellulose chromatography into a catalytic component of Mr = 19,000 and a complex comprised of the catalytic component associated with the natural phosphate-acceptor protein of Mr = 70,000. This protein kinase was not activated by cyclic nucleotides or calcium ion.