Percy A K, Carson M A, Moore J F, Waechter C J
Arch Biochem Biophys. 1984 Apr;230(1):69-81. doi: 10.1016/0003-9861(84)90087-0.
Membrane preparations from Saccharomyces cerevisiae catalyze the transfer of phosphoethanolamine and phosphocholine from the cytidine dinucleotide derivatives to endogenous and exogenous 1,2-diacylglycerols. Utilizing CDP-[14C]ethanolamine and CDP-[14C]choline as isotopic substrates, diacylglycerol ethanolaminephosphotransferase (EPT) and diacylglycerol cholinephosphotransferase (CPT) have been characterized in vitro. Both enzymes (i) require Mn2+; (ii) are stimulated by exogenous 1,2-diacylglycerols; and (iii) are inhibited by p-hydroxymercuribenzoate and CMP. Yeast EPT and CPT can be clearly distinguished on the basis of their different (i) pH optima; (ii) thermal sensitivities at 50 degrees C; (iii) concentration-dependent inhibition by CMP; and (iv) sensitivities to the hypolipidemic drug, DH-990. Reversibility experiments demonstrate that CDP-ethanolamine can be resynthesized by enzymatic reactions involving CMP and phosphatidylethanolamine (PE) formed from the cytidine dinucleotide derivative or by the decarboxylation of phosphatidylserine (PS). Similarly, CDP-choline can be reformed by the reaction of CMP with PC synthesized from CDP-choline or by the sequential N-methylation of PE. A double-isotope experiment provides evidence that PE molecules synthesized via CDP-ethanolamine or by the decarboxylation of PS are converted to phosphatidylcholine (PC) by the methylation pathway at similar, if not identical, rates. The N-methylation of the metabolically specific pool of PE, synthesized from CDP-ethanolamine, is drastically reduced in membranes prepared from choline-grown cells. Neither EPT nor CPT appear to be induced by the addition of ethanolamine or choline, respectively, to the growth medium. However, the addition of 10 mM choline to the growth medium results in a 46% reduction in EPT activity. This change in EPT activity may be a regulatory response to lower rates of PE N-methylation in choline-grown cells.
来自酿酒酵母的膜制剂催化磷酸乙醇胺和磷酸胆碱从胞苷二核苷酸衍生物转移至内源性和外源性1,2 - 二酰基甘油。利用CDP - [14C]乙醇胺和CDP - [14C]胆碱作为同位素底物，已在体外对二酰基甘油乙醇胺磷酸转移酶（EPT）和二酰基甘油胆碱磷酸转移酶（CPT）进行了表征。这两种酶：（i）都需要Mn2 +；（ii）受到外源性1,2 - 二酰基甘油的刺激；（iii）受到对羟基汞苯甲酸和CMP的抑制。酵母EPT和CPT可以基于它们不同的（i）最适pH值；（ii）50℃时的热敏感性；（iii）CMP的浓度依赖性抑制；以及（iv）对降血脂药物DH - 990的敏感性而被清楚地区分。可逆性实验表明，CDP - 乙醇胺可以通过涉及CMP和由胞苷二核苷酸衍生物形成的磷脂酰乙醇胺（PE）的酶促反应或通过磷脂酰丝氨酸（PS）的脱羧作用重新合成。同样，CDP - 胆碱可以通过CMP与由CDP - 胆碱合成的PC的反应或通过PE的顺序N - 甲基化而重新形成。一项双同位素实验提供了证据，表明通过CDP - 乙醇胺或PS脱羧作用合成的PE分子通过甲基化途径以相似（如果不是相同）的速率转化为磷脂酰胆碱（PC）。从胆碱培养的细胞制备的膜中，由CDP - 乙醇胺合成的代谢特异性PE池的N - 甲基化显著降低。分别向生长培养基中添加乙醇胺或胆碱似乎均不会诱导EPT或CPT。然而，向生长培养基中添加10 mM胆碱会导致EPT活性降低46％。EPT活性的这种变化可能是对胆碱培养的细胞中PE N - 甲基化速率降低的一种调节反应。
