磷脂酰肌醇激酶。嗜铬粒膜的一个组成部分。
Phosphatidylinositol kinase. A component of the chromaffin-granule membrane.
作者信息
Phillips J H
出版信息
Biochem J. 1973 Nov;136(3):579-87. doi: 10.1042/bj1360579.
Phosphorylation of bovine chromaffin granules by ATP leads to the formation of diphosphoinositide in the granule membrane. Both phosphatidylinositol kinase and its substrate are components of this membrane, and triphosphoinositide is not formed under the conditions of the assay. The reaction is Mg(2+)-dependent and is stimulated by Mn(2+) and F(-) ions. The initial reaction is rapid, with a broad pH profile and a ;transition' temperature for its activation energy at 27 degrees C. The apparent K(m) for ATP is 5mum. ATP, N-ethylmaleimide, Cu(2+) ions and NaIO(4) are inhibitory. The phospholipids of chromaffin-granule membranes have been analysed: 6.8% of the lipid P is found in phosphatidylinositol, and only 2-3% in phosphatidylserine. Comparison of the rate of phosphorylation of intact and lysed granules suggests that the sites for phosphorylation are on the outer (cytoplasmic) surface of the granules, and diphosphoinositide may therefore make an important contribution to the charge of the chromaffin granule in vivo.
ATP 对牛嗜铬颗粒的磷酸化作用导致颗粒膜中双磷酸肌醇的形成。磷脂酰肌醇激酶及其底物均为该膜的组成成分，且在测定条件下不会形成三磷酸肌醇。该反应依赖 Mg(2+)，并受到 Mn(2+) 和 F(-) 离子的刺激。初始反应迅速，具有较宽的 pH 范围，其活化能在 27℃ 时有一个“转变”温度。ATP 的表观 K(m) 为 5μm。ATP、N - 乙基马来酰亚胺、Cu(2+) 离子和 NaIO(4) 具有抑制作用。已对嗜铬颗粒膜的磷脂进行了分析：发现 6.8% 的脂质 P 存在于磷脂酰肌醇中，而磷脂酰丝氨酸中仅占 2 - 3%。完整颗粒和裂解颗粒磷酸化速率的比较表明，磷酸化磷酸化位点位于颗粒的外（细胞质）表面，因此双磷酸肌醇可能在体内对嗜铬颗粒的电荷起重要作用。
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