Litosch I
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, FL 33101, USA.
Recept Signal Transduct. 1996;6(2):87-98.
Protein kinase C (PKC) inhibited the Ca(2+)-dependent stimulation of a 600-fold purified phospholipase C beta 1 (PLC-beta 1). Inhibition by PKC was time-dependent, and required ATP and diacylglycerol. Inhibition was more pronounced when the PLC assay was conducted with a PIP2 substrate mixture containing phosphatidylserine, then with a substrate mixture containing phosphatidyle-thanolamine. Cyclic AMP-dependent protein kinase A did not inhibit PLC-beta 1 activity. PKC did not affect the rate of PLC-beta 1 activation by Ca2+ or the rate of PLC-beta 1 deactivation by EGTA. PLC-beta 1 purified 1700-fold was less sensitive to inhibition by PKC despite stoichiometric phosphorylation. These results demonstrate that PKC inhibits the Ca(2+)-dependent stimulation of a 600-fold purified PLC-beta 1 in vitro. Furthermore, purification of PLC-beta 1 to homogeneity results in a diminished sensitivity to inhibition by PKC, indicating that other components may participate in mediating the effect of PKC on the Ca(2+)-dependent stimulation of PLC-beta 1 in vitro.
蛋白激酶C（PKC）抑制了经600倍纯化的磷脂酶Cβ1（PLC-β1）的钙依赖性刺激作用。PKC的抑制作用具有时间依赖性，且需要ATP和二酰基甘油。当使用含有磷脂酰丝氨酸的PIP2底物混合物进行PLC测定时，抑制作用比使用含有磷脂酰乙醇胺的底物混合物时更为明显。环磷酸腺苷依赖性蛋白激酶A不抑制PLC-β1的活性。PKC不影响Ca2+对PLC-β1的激活速率或EGTA对PLC-β1的失活速率。尽管进行了化学计量的磷酸化，但经1700倍纯化的PLC-β1对PKC抑制的敏感性较低。这些结果表明，PKC在体外抑制经600倍纯化的PLC-β1的钙依赖性刺激作用。此外，将PLC-β1纯化至同质状态会导致其对PKC抑制的敏感性降低，这表明其他成分可能参与介导PKC对体外PLC-β1钙依赖性刺激作用的影响。
