Phosphatidylinositol Kinase Activation Mechanism by Growth Factors

为了阐明生长因子的作用机制，我们对参与生长因子信号转导的酶进行了纯化。酪氨酸激酶与肌醇磷脂信号转导系统之间的相互作用是近年来研究的热点。PI 4-激酶是催化PIP 2合成的关键酶，PIP 2水解为IP 3和DG。这些物质充当各种细胞反应的第二信使。我们从大鼠脑组织中纯化了PI 4-激酶，并测定了其部分氨基酸序列。其次，我们分离了编码PI 4-激酶的DNA克隆，并推导了其总氨基酸序列。该蛋白质与迄今发现的其他蛋白质没有任何同源性。PI 3-激酶在细胞生长的信号转导中起重要作用。该酶也从牛胸腺中纯化。分离出两种PI 3激酶。它们的分子量分别为190 KDa和110 KDa。190 KDa蛋白质由110 KDa和80 KDa两部分组成。这些结果表明，有两个PI 3激酶。一种是单体，另一种是异二聚体。MdR型比异二聚体形式具有更高的活性。

We purified enzymes involved in signal transduction of growth factors to clarify the action mechanism of growth factors. Recently much attention has been paid on the cross talk between tyrosine kinase and inositolphospholipid signaling system. PI4-kinase is a key enzyme which catalyze the synthesis of PIP2, which is hydrolyzed to IP3 and DG. These substances are acting as second messengers for various cellular responses. We purified PI4-kinase from rat brain and determined the partial aminoacid sequence of the protein. Next, we isolated thecDNA clone encoded PI4-kinase and deduced the total aminoacid sequence. The protein did not have any homology to other proteins so far discovered. PI3-kinase hasbeen considered to play important role in signal transduction of cell growth. This enzyme was also purified from bovine thymus. Two PI3-kinases were isolated. Their molecular weights were 190 KDa and 110KDa, respectively. The protein (190KDa) consisted of 110 KDa and 80 KD a protein. These results suggest that there are two PI3 kinases. One is monomer and another is heterodimer. Monomer type has higher activity than heterodimer form.