Human phosphoinositide 3-kinase C2β, the role of calcium and the C2 domain in enzyme activity
Human phosphoinositide 3-kinase C2β, the role of calcium and the C2 domain in enzyme activity
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DOI：
10.1074/jbc.273.49.33082
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发表时间：
1998-12-04
影响因子：
4.8
通讯作者：
Waterfield, MD
中科院分区：
文献类型：
--
作者：
Arcaro, A;Volinia, S;Waterfield, MD
从U937单核细胞cDNA文库中克隆具有C2结构域的人II类磷酸肌醇3-激酶（PI 3-激酶C2 β）的cDNA，并在哺乳动物和昆虫细胞中表达该酶。与体外其他II类PI 3-激酶一样，PI 3-激酶C2 β在Mg 2+存在下利用磷脂酰肌醇（PI）和PI 4-单磷酸而不是PI 4，5-二磷酸作为底物。值得注意的是，与其他PI 3-激酶不同，该酶可以使用Mg-ATP或Ca-ATP来产生PI 3-单磷酸。PI 3-激酶C2 β与I类PI 3-激酶相似，但与PI 3-激酶C2 α不同，对低纳摩尔水平的抑制剂渥曼青霉素敏感。该酶不受小GTP结合蛋白Pas的调节。该酶的C2结构域在体外结合阴离子磷脂如PI和磷脂酰丝氨酸，但不协同结合Ca 2+和磷脂。C2结构域的缺失增加了脂质激酶活性，表明其作为催化结构域的负调节剂起作用。虽然目前尚不清楚PI 3-激酶C2 β是否受体内Ca 2+的调节，但我们的研究结果表明Ca 2+离子在磷酸盐转移反应中具有新的作用。
The cDNA for a human Class II phosphoinositide 3-kinase (PI 3-kinase C2 beta) with a C2 domain was cloned from a U937 monocyte cDNA library and the enzyme expressed in mammalian and insect cells. Like other Class II PI 3-kinases in vitro, PI 3-kinase C2 beta utilizes phosphatidylinositol (PI) and PI 4-monophosphate but not PI 4,5-biphosphate as substrates in the presence of Mg2+. Remarkably, and unlike other PI 3-kinases, the enzyme can use either Mg-ATP or Ca-ATP to generate PI 3-monophosphate. PI 3-kinase C2 beta, like the Class I PI 3-kinases, but unlike PI 3-kinase C2 alpha, is sensitive to low nanomolar levels of the inhibitor wortmannin. The enzyme is not regulated by the small GTP-binding protein Pas. The C2 domain of the enzyme bound anionic phospholipids such as PI and phosphatidylserine in vitro, but did not co-operatively bind Ca2+ and phospholipids. Deletion of the C2 domain increased the lipid kinase activity suggesting that it functions as a negative regulator of the catalytic domain. Although presently it is not known whether PI 3-kinase C2 beta is regulated by Ca2+ in vivo, our results suggest a novel role for Ca2+ ions in phosphate transfer reactions.