Synthetic seminal plasma peptide influences angiotensin converting enzyme retention in the plasma membrane

Aim: The retention of angiotensin converting enzyme (ACE) in the plasma membrane is regulated by casein kinase II (CK2)-mediated phosphorylation. The endothelial cells treated with CK2 inhibitor decreased the ACE phosphorylation and increased its shedding. Seminal plasma peptide (pGlu-Val-Ala-Asp-Ser-Asp-Gln-Asn), synthesized following data obtained from biochemical and mass spectrometry analysis of highly purified fraction from bovine seminal plasma, was demonstrated to be a substrate of CK2. The aim of our research was to study whether synthetic seminal plasma peptide competes with ACE in CK2 phosphorylation influencing ACE shedding. Methods: GC-1spg, mouse spermatogonia cell line, and ECV304, human umbilical cord transformed endothelium, expressing testicular ACE and somatic ACE, respectively, were incubated for 24 h at 37°C with increased doses of synthetic seminal plasma peptide. ACE activity was measured by following the hydrolyzing activity of the cell homogenates on FAPGG, a synthetic substrate of somatic and testicular ACE. Results: The preliminary data show a dose-dependent decrease of ACE activity in both cell lines after the treatment with synthetic seminal plasma peptide. This residual activity is lower in GC-1spg cell line (33% of ACE activity vs control at 10-8M peptide concentration) than in ECV304 cell line (54% of ACE activity vs control at 10-8M peptide concentration). Conclusions: These preliminary results suggest the possible role of synthetic seminal plasma peptide in the control on testicular and somatic ACE release from plasma membrane.