出版社：American Society for Biochemistry and Molecular Biology
摘要：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 Mg2+, Ni2+, Co2+, and Mn2+. The pH optimum is 7.2. The enzyme is stable to heating at 50°C for 15 min and is insensitive to sulfhydryl inhibitors. Glycerophosphoryl diesters of choline, ethanolamine, inositol, serine, glycerol, and β-methylcholine are hydrolyzed to the common product, l -α-glycerophosphate, and the appropriate free alcohol. The rate of glycerophosphorylcholine hydrolysis is 70% greater than the rate of hydrolysis of the other glycerophosphodiesters. Apparent Km , values for glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphoryl-β-methylcholine are 2–4 × 10–4 m , and for glycerophosphorylinositol, 2 × 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 -α-glycerophosphate, exchanges into glycerophosphorylcholine and glycerophosphorylinositol.
