Chakrabarti A K, Dasgupta S, Gadsden R H, Hogan E L, Banik N L
Department of Neurology, Medical University of South Carolina, Charleston 29425, USA.
J Neurosci Res. 1996 May 15;44(4):374-80. doi: 10.1002/(SICI)1097-4547(19960515)44:4<374::AID-JNR9>3.0.CO;2-9.
Combinations of certain phospholipids and gangliosides increase the specific activity of m calpain and can activate m calpain at 1 to 10 microM Ca2+ concentration. However, this level of calcium is still greater than the normal intracellular calcium level. We have used combinations of lipids to demonstrate the m calpain activity at the physiological Ca2+ level. GD1a (100 microM) and cerebroside (Cerb; 750 microM; 1:7.5) mixture was the most effective. At 0.5 microM to 1.0 microM Ca2+ concentrations, 15-20% of the maximal activity was detected for the purified myelin and cytosolic m calpains. Other combinations were GD1a (100 microM), GM1 (100 microM), Cerb (750 microM), sulfatide (Sulf; 750 microM), and phosphatidylinositol (PI; 300 microM) at a ratio of 1:1: 7.5:7.5:3, respectively. These lipid mixtures stimulated calpain activity at three- to tenfold less calcium concentration than control. The other mixtures, including GD1a:Sulf (1:9) > GD1a:PI (1:4) > PI:Sulf (1:5) > Cerb:Sulf (1:5) and PI:Cerb (1:2.5), also stimulated calpain activity at 1.0 microM Ca2+ concentration. Triton X-100, oxidized glutathione (GSSG), and calpain activator did not affect the Ca2+ requirement. Liposomes containing GD1a, Cerb, and m calpain also showed recognizable calpain activity at a significantly reduced Ca2+ concentration (0.4 microM), confirming the glycolipid-mediated enzyme modulation. These studies indicate that specific lipid mixtures can stimulate m calpain activity at an intracellular level of Ca2+.
某些磷脂和神经节苷脂的组合可提高m钙蛋白酶的比活性，并能在1至10微摩尔/升的钙离子浓度下激活m钙蛋白酶。然而，这个钙水平仍高于正常细胞内钙水平。我们已使用脂质组合来证明在生理钙离子水平下的m钙蛋白酶活性。GD1a（100微摩尔/升）和脑苷脂（Cerb；750微摩尔/升；1:7.5）的混合物最为有效。在0.5至1.0微摩尔/升的钙离子浓度下，纯化的髓鞘和胞质m钙蛋白酶可检测到最大活性的15%至20%。其他组合分别为GD1a（100微摩尔/升）、GM1（100微摩尔/升）、Cerb（750微摩尔/升）、硫苷脂（Sulf；750微摩尔/升）和磷脂酰肌醇（PI；300微摩尔/升），比例为1:1:7.5:7.5:3。这些脂质混合物在比对照低三至十倍的钙浓度下刺激钙蛋白酶活性。其他混合物，包括GD1a:Sulf（1:9）> GD1a:PI（1:4）> PI:Sulf（1:5）> Cerb:Sulf（1:5）和PI:Cerb（1:2.5），在1.0微摩尔/升的钙离子浓度下也刺激钙蛋白酶活性。曲拉通X - 100、氧化型谷胱甘肽（GSSG）和钙蛋白酶激活剂不影响对钙离子的需求。含有GD1a、Cerb和m钙蛋白酶的脂质体在显著降低的钙离子浓度（0.4微摩尔/升）下也显示出可识别的钙蛋白酶活性，证实了糖脂介导的酶调节作用。这些研究表明，特定的脂质混合物可在细胞内钙离子水平刺激m钙蛋白酶活性。
