Hildenbrandt G R, Bieber L L
J Lipid Res. 1972 May;13(3):348-55.
Homogenates of Musca domestica (housefly) larvae contain glycerophosphodiesterase activity, which is found in the supernatant fluid after centrifugation at 88,000 g. The phosphodiesterase is inhibited by EDTA and is stimulated by Mg(2+), Ni(2+), Co(2+), and Mn(2+). The pH optimum is 7.2. The enzyme is stable to heating at 50 degrees C for 15 min and is insensitive to sulfhydryl inhibitors. Glycerophosphoryl diesters of choline, ethanolamine, inositol, serine, glycerol, and beta-methylcholine are hydrolyzed to the common product, l-alpha-glycerophosphate, and the appropriate free alcohol. The rate of glycerophosphorylcholine hydrolysis is 70% greater than the rate of hydrolysis of the other glycerophosphodiesters. Apparent K(m) values for glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphoryl-beta-methylcholine are 2-4 x 10(-4) m, and for glycerophosphorylinositol, 2 x 10(-3) m. Competitive studies using various pairs of substrates, as well as the exchange of free choline into both glycerophosphorylcholine and glycerophosphorylinositol, suggest that a single enzyme cleaves all substrates. Product inhibition and reversal of the reaction were not detected. Choline, but not l-alpha-glycerophosphate, exchanges into glycerophosphorylcholine and glycerophosphorylinositol.
家蝇幼虫的匀浆含有甘油磷酸二酯酶活性，该活性在88,000g离心后的上清液中被发现。磷酸二酯酶受EDTA抑制，并被Mg(2+)、Ni(2+)、Co(2+)和Mn(2+)激活。最适pH为7.2。该酶在50℃加热15分钟后稳定，对巯基抑制剂不敏感。胆碱、乙醇胺、肌醇、丝氨酸、甘油和β-甲基胆碱的甘油磷酸二酯被水解为共同产物l-α-甘油磷酸和相应的游离醇。甘油磷酸胆碱的水解速率比其他甘油磷酸二酯的水解速率高70%。甘油磷酸胆碱、甘油磷酸乙醇胺和甘油磷酸-β-甲基胆碱的表观K(m)值为2-4×10(-4)m，甘油磷酸肌醇的表观K(m)值为2×10(-3)m。使用各种底物对进行的竞争性研究，以及游离胆碱与甘油磷酸胆碱和甘油磷酸肌醇之间的交换，表明单一酶可裂解所有底物。未检测到产物抑制和反应逆转。胆碱可与甘油磷酸胆碱和甘油磷酸肌醇进行交换，但l-α-甘油磷酸不能。
