Biosynthesis of phosphatidylcholine by enzyme preparations from spinach leaves
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چکیده
The enzymic incorporation of choline-l,2-'C from CDP-choline-1 ,V4C into phosphatidylcholine by spinach leaf preparations was characterized. The enzyme catalyzing the incorporation, choline phosphotransferase, had a pH optimum of about 8.0 and required either Mn2+ or Mg2+ as cofactor. The saturation concentration of Mn2+ was 0.3 mM and that for Mg2+ was 13 mM. The nT, for CDP-choline was 10 p ~ . The choline phosphotransferase was inhibited by sulfhydryl reagents. The enzyme was inactivated at 3OoC, but this inactivation could be prevented by dithiothreitol and Mn*+. Preincubation of the enzyme with Mn2+ prevented inhibition by sulfhydryl reagents. The incorporation of diglyceride-U-'C into phosphatidylcholine was also studied. The enzyme did not show any diglyceride specificity when exogenous diglyceride was added, indicating that fatty acid distribution in phosphatidylcholine of spinach is not controlled by choline phosphotransferase. SUPPLEMENTARY
منابع مشابه
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