title: Inhibition by gossypol of phospholipid-sensitive Ca2+-dependent protein kinase from pig testis.
abstract: Gossypol, a polyphenolic binaphthalene-dialdehyde extracted from cotton plants which possesses male antifertility action in mammals, is a potent inhibitor of phospholipid-sensitive Ca2+-dependent protein kinase from pig testis. Gossypol inhibited Ca2+-dependent activity of the enzyme without affecting its basal activity. The IC50 value (concentration causing 50% inhibition) was 31 microM when lysine-rich histone was used as substrate. Kinetic analysis indicated that the compound inhibited the enzyme non-competitively with respect to ATP (Ki = 31 microM) or lysine-rich histone (Ki = 30 microM), and competitively with respect to phosphatidylserine (Ki = 2.1 microM). With Ca2+, irrespective of the presence or absence of 1,3-diolein, the compound lowered Vmax and increased the apparent Ka for Ca2+. The compound also inhibited phosphorylation by the enzyme of high-mobility-group 1 protein (one of the endogenous substrates in the testis for the enzyme located in nucleosome), with an IC50 value of 88 microM. These results suggested that a phospholipid-sensitive Ca2+-dependent protein phosphorylation system in the testis is involved in the regulation of spermatogenesis.
authors.forename: K
authors.initials: K
authors.lastname: Kimura
authors.forename: K
authors.initials: K
authors.lastname: Sakurada
authors.forename: N
authors.initials: N
authors.lastname: Katoh
mesh_terms: D000818:Animals; D006072:Gossypol / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D010766:Phosphorylation; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D013091:Spermatogenesis / Q000187:drug effects; D013552:Swine; D013737:Testis / Q000201:enzymology*
chemical_list: D047428:Protein Kinase Inhibitors; D011493:Protein Kinase C; D006072:Gossypol