Martiny-Baron G, Kazanietz M G, Mischak H, Blumberg P M, Kochs G, Hug H, Marmé D, Schächtele C
Department of Biochemical Pharmacology, Gödecke AG, Freiburg, Germany.
J Biol Chem. 1993 May 5;268(13):9194-7.
Indolocarbazoles have been identified as novel inhibitors of protein kinase C (PKC), with Gö 6976 as one of its most potent and selective representatives. Recombinant PKC isozymes alpha, beta 1, delta, epsilon, and zeta were used in in vitro kinase assays to investigate Gö 6976 with respect to isozyme-specific PKC inhibition. Gö 6850, identical with GF 109203X, another PKC-specific kinase inhibitor, was included in this study as a reference compound. Nanomolar concentrations of the indolocarbazole Gö 6976 inhibited the Ca(2+)-dependent isozymes alpha and beta 1, whereas even micromolar concentration of Gö 6976 had no effect on the kinase activity of the Ca(2+)-independent PKC subtypes delta, epsilon, and zeta. In contrast, the bisindolymaleimide Gö 6850 inhibited all PKC isozymes, however, with a ranked order of potency (alpha > beta 1 > epsilon > delta > zeta). Kinetic analysis revealed that PKC inhibition by Gö 6976 was competitive with respect to ATP, non-competitive with respect to the protein substrate, and mixed type with respect to phosphatidylserine. Further experiments in the presence of different amounts of free Ca2+ indicated that interference with Ca2+ or its binding site is not responsible for the differential inhibition of PKC isozymes by Gö 6976.
吲哚咔唑已被确定为蛋白激酶C（PKC）的新型抑制剂，Gö 6976是其最有效和最具选择性的代表之一。在体外激酶测定中使用重组PKC同工酶α、β1、δ、ε和ζ来研究Gö 6976对同工酶特异性PKC的抑制作用。Gö 6850与另一种PKC特异性激酶抑制剂GF 109203X相同，作为参考化合物纳入本研究。纳摩尔浓度的吲哚咔唑Gö 6976抑制了依赖Ca(2+)的同工酶α和β1，而即使是微摩尔浓度的Gö 6976对不依赖Ca(2+)的PKC亚型δ、ε和ζ的激酶活性也没有影响。相比之下，双吲哚马来酰亚胺Gö 6850抑制了所有PKC同工酶，但其抑制效力顺序为（α>β1>ε>δ>ζ）。动力学分析表明，Gö 6976对PKC的抑制作用在ATP方面是竞争性的，在蛋白质底物方面是非竞争性的，在磷脂酰丝氨酸方面是混合型的。在存在不同量游离Ca2+的情况下进行的进一步实验表明，Gö 6976对PKC同工酶的差异抑制作用不是由于干扰Ca2+或其结合位点所致。
