Cyclic adenosine monophosphate-dependent protein kinases of human seminal plasma: origin and characteristics of multiple forms

It was recently demonstrated that the protein kinase activity of human seminal plasma was cAMP-independent. However, the authors have been able to show that 90 to 95% of the respective enzyme activity: 1) originates from intra-spermatozoal cAMP-dependent protein kinase pools, 2) can be classified as cAMP-dependent protein kinases, and 3) rapidly loses its cAMP dependency due to proteolytic activities of seminal plasma. The author's results strongly indicate that the protein kinase activity of human seminal plasma is not an intrinsic component of this fluid, that it is not produced by the accessory male gland secretions, and that it may originate from the spermatozoa during semen liquefaction.