摘要
Protein kinase C with a molecular weight of 82 kD has been purified to electrophoresis homogenous from rat brain through a series of chromatography columns including DE-52, Sepharose G-200 and phenyl-Sepharose. The enzyme possessed autophosphorylation activity. Yuanhuacin A inhibited the <sup>3</sup>H-phorbol-12, 13-dibutyrate （<sup>3</sup>H-PdBu） binding of PKC with an IC<sub>50</sub> value of 1.48±0.28×10<sup>-8</sup> mol/L when the concentration of <sup>3</sup>H-PdBu was 1.5×10<sup>-9</sup> mol/L (K<sub>i</sub>=1.2×10<sup>-8</sup> mol/L). Yuanhuacin A inhibited the PdBu-stimulated PKC activity in the catalysis of the phosphorylation of Histone Ⅲ-S with an IC<sub>50</sub> of 2.82±0.37×10<sup>-9</sup> mol/L (PdBu=10<sup>-6</sup> mol/L), while it had no effect on the basal and Ca<sup>2+</sup>-stimulated PKC activity in the same assay system. This result suggests that Yuanhuacin A is a selective antagonist of the phorbol ester receptor in protein kinase C.
Protein kinase C with a molecular weight of 82 kD has been purified to electrophoresis homogenous from rat brain through a series of chromatography cohmns including DE-52, Sepharose G-200 and phenyl-Sepharose. The enzyme possessed autophosphorylation activity. Yuanhuacin A inhibited the ~3H-phorbol-12, 13-dibutyrate (~3H-PdBu) binding of PKC with an IC_(50) value of 1.48±0.287×10^(-8) mol/L when the concentration of ~3H-PdBu was 1.5×10^(-9) mol/L (K_i=1.2×10^(-8) mol/L). Yuanhuacin A inhibited the PdBu-stimulated PKC activity in the catalysis of the phosphorylation of Histone Ⅲ-S with an IC_(50) of 2.82±0.37×10^(-9) mol/L (PdBu=10^(-6) mol/L), while it had no effect on the basal and Ca^(2+)-stimulated PKC activity in the same assay system. This result suggests that Yuanhuacin A is a selective antagonist of the phorbol ester receptor in protein kinase C.
