Liteplo R G, Sribney M
Can J Biochem. 1977 Oct;55(10):1049-56. doi: 10.1139/o77-156.
The properties of rat liver microsomal CDPethanolamine: 1,2-diacylglycerol ethanolamine-phosphotransferase (ethanolaminephosphotransferase; EC 2.7.8.1) are studied with respect to metal ion and substrate concentration. The enzyme requires magnesium (20 mM) or manganese (1 mM) ions for optimum activity. Manganese ions are better activators of ethanolaminephosphotransferase activity than are magnesium ions. Calcium 1 mM) inhibits the magnesium-activated ethanolaminephosphotransferase by 86% and the manganese-activated enzyme by 57%. The Km for CDPethanolamine is 2.4 and 0.7 x 10(-4) M, in the presence of magnesium or manganese ions, respectively. ATP plus pantetheine significantly inhibit the manganese-activated ethanolaminephosphotransferase, while the magnesium-activated enzyme is inhibited by ATP plus pantetheine and slightly stimulated by ATP plus CoA. In the presence of either metal ion, ATP itself inhibits enzyme activity, while CoA or pantetheine when added alone have no effect. Evidence is presented indicating that the inhibition of ethanolaminephosphotransferase activity by ATP plus CoA or ATP plus pantetheine is not due to the formation of acyl-CoA or acyl-S-pantetheine esters. At the present time, however, the true mechanism of inhibition is unknown. The results indicate that the cellular levels of ATP, CoA, pantetheine, magnesium, manganese, and calcium ions may all play a role in the regulation of phosphatidylethanolamine biosynthesis.
对大鼠肝脏微粒体CDP乙醇胺：1,2 - 二酰甘油乙醇胺 - 磷酸转移酶（乙醇胺磷酸转移酶；EC 2.7.8.1）的性质进行了金属离子和底物浓度方面的研究。该酶需要镁离子（20 mM）或锰离子（1 mM）以达到最佳活性。锰离子比镁离子更能激活乙醇胺磷酸转移酶的活性。钙离子（1 mM）可使镁离子激活的乙醇胺磷酸转移酶活性抑制86%，使锰离子激活的酶活性抑制57%。在存在镁离子或锰离子的情况下，CDP乙醇胺的Km值分别为2.4和0.7×10⁻⁴ M。ATP加泛硫乙胺能显著抑制锰离子激活的乙醇胺磷酸转移酶，而镁离子激活的酶则被ATP加泛硫乙胺抑制，并被ATP加辅酶A轻微刺激。在存在任何一种金属离子的情况下，ATP本身会抑制酶活性，而单独添加辅酶A或泛硫乙胺则无影响。有证据表明，ATP加辅酶A或ATP加泛硫乙胺对乙醇胺磷酸转移酶活性的抑制并非由于酰基辅酶A或酰基 - S - 泛硫乙胺酯的形成。然而，目前抑制的真正机制尚不清楚。结果表明，细胞内ATP、辅酶A、泛硫乙胺、镁离子、锰离子和钙离子的水平可能都在磷脂酰乙醇胺生物合成的调节中发挥作用。
