Souvignet C, Chambaz E M
INSERM U 244 LBIO, Département de Recherche Fondamentale, Centre d'Etudes Nucléaires, Grenoble, France.
Cell Signal. 1990;2(2):171-6. doi: 10.1016/0898-6568(90)90020-b.
The ability of purified protein kinase C (PKC) to phosphorylate protamine sulphate was found to be totally independent of phospholipid cofactors, whereas the phosphorylation of protamine free base was markedly increased by the presence of phosphatidylserine (PS). The hypothesis of an activation of PKC by the sulphate groups of protamine sulphate was confirmed by the high phosphorylation of protamine free base in the presence of non-peptide polyanionic compounds, such as glycoaminoglycans or polynucleotides. The catalytic fragment of PKC supported protamine base phosphorylation with the same polyanionic dependency. Light scattering intensity measurements showed that this phosphorylation correlated to the substrate/cofactor aggregation. These data support the view that apparent phospholipid-independent activation of PKC results from the formation of aggregates in the assay and this could result in the non-specific activation of this enzyme through its catalytic domain.
研究发现，纯化的蛋白激酶C（PKC）磷酸化硫酸鱼精蛋白的能力完全独立于磷脂辅因子，而磷脂酰丝氨酸（PS）的存在则显著增加了游离鱼精蛋白碱的磷酸化。硫酸鱼精蛋白的硫酸基团激活PKC这一假说，在存在非肽多阴离子化合物（如糖胺聚糖或多核苷酸）的情况下，游离鱼精蛋白碱的高磷酸化得到了证实。PKC的催化片段支持游离鱼精蛋白碱的磷酸化，且具有相同的多阴离子依赖性。光散射强度测量表明，这种磷酸化与底物/辅因子聚集相关。这些数据支持这样一种观点，即PKC明显的非磷脂依赖性激活是由于测定中聚集体的形成，这可能通过其催化结构域导致该酶的非特异性激活。
