Ancelin M L, Vial H J
FEBS Lett. 1986 Jul 7;202(2):217-23. doi: 10.1016/0014-5793(86)80690-1.
In Plasmodium falciparum-infected erythrocyte homogenates, the specific activity of ethanolamine kinase (7.6 +/- 1.4 nmol phosphoethanolamine/10(7) infected cells per h) was higher than choline kinase specific activity (1.9 +/- 0.2 nmol phosphocholine/10(7) infected cells per h). The Km of choline kinase for choline was 79 +/- 20 microM, and ethanolamine was a weak competitive inhibitor of the reaction (Ki = 92 mM). Ethanolamine kinase had a Km for ethanolamine of 188 +/- 19 microM, and choline was a competitive inhibitor of ethanolamine kinase with a very high Ki of 268 mM. Hemicholinium 3 inhibited choline kinase activity, but had no effect on ethanolamine kinase activity. In contrast, D-2-amino-1-butanol selectively inhibited ethanolamine kinase activity. Furthermore, when the two enzymes were subjected to heat inactivation, 85% of the choline kinase activity was destroyed after 5 min at 50 degrees C, whereas ethanolamine kinase activity was not altered. Our results indicate that the phosphorylation of choline and ethanolamine was catalyzed by two distinct enzymes. The presence of a de novo phosphatidylethanolamine Kennedy pathway in P. falciparum contributes to the bewildering variety of phospholipid biosynthetic pathways in this parasitic organism.
在恶性疟原虫感染的红细胞匀浆中，乙醇胺激酶的比活性（7.6±1.4 nmol磷酸乙醇胺/10⁷个感染细胞每小时）高于胆碱激酶的比活性（1.9±0.2 nmol磷酸胆碱/10⁷个感染细胞每小时）。胆碱激酶对胆碱的Km值为79±20 μM，乙醇胺是该反应的弱竞争性抑制剂（Ki = 92 mM）。乙醇胺激酶对乙醇胺的Km值为188±19 μM，胆碱是乙醇胺激酶的竞争性抑制剂，其Ki值非常高，为268 mM。半胱氨酸3抑制胆碱激酶活性，但对乙醇胺激酶活性无影响。相反，D-2-氨基-1-丁醇选择性抑制乙醇胺激酶活性。此外，当这两种酶进行热失活时，50℃下5分钟后85%的胆碱激酶活性被破坏，而乙醇胺激酶活性未改变。我们的结果表明，胆碱和乙醇胺的磷酸化由两种不同的酶催化。恶性疟原虫中从头合成磷脂酰乙醇胺的肯尼迪途径的存在，导致了这种寄生生物中磷脂生物合成途径的多样性令人困惑。
