Macher B A, Mudd J B
Department of Biochemistry and Statewide Air Pollution Research Center, University of California, Riverside, California 92502.
Plant Physiol. 1974 Feb;53(2):171-5. doi: 10.1104/pp.53.2.171.
The enzymic utilization of cytidine diphosphoethanolamine in the synthesis of phosphatidylethanolamine is localized in the microsomal fraction of spinach (Spinacia oleracea) leaves. The metal ion requirement can be satisfied by Mn(2+) (saturation approximately 0.6 mm) or Mg(2+) (saturation approximately 25 mm). The enzyme has a pH optimum of 8.0 in the presence of Mn(2+) and 7.5 in the presence of Mg(2+). A Michaelis constant of 20 mum was determined for cytidinediphos-phoethanolamine. Enzyme activity was stimulated by thiol compounds and inhibited by thiol reagents. No inhibition was obtained with cytidine monophosphate and Tween 80.The in vitro biosynthesis of phosphatidylethanolamine was inhibited by cytidine diphosphocholine and the biosynthesis of phosphatidylcholine was inhibited by cytidine diphosphoethanolamine. Activities of the two synthetic systems were indistinguishable on the basis of susceptibility to lyophilization and inhibition by thiol reagents.
胞苷二磷酸乙醇胺在磷脂酰乙醇胺合成中的酶促利用定位于菠菜（Spinacia oleracea）叶片的微粒体部分。金属离子需求可由Mn(2+)（饱和度约0.6 mM）或Mg(2+)（饱和度约25 mM）满足。该酶在存在Mn(2+)时的最适pH为8.0，在存在Mg(2+)时为7.5。测定胞苷二磷酸乙醇胺的米氏常数为20 μM。酶活性受硫醇化合物刺激，受硫醇试剂抑制。胞苷一磷酸和吐温80未产生抑制作用。磷脂酰乙醇胺的体外生物合成受胞苷二磷酸胆碱抑制，磷脂酰胆碱的生物合成受胞苷二磷酸乙醇胺抑制。基于对冻干的敏感性和硫醇试剂的抑制作用，两个合成系统的活性无法区分。
