Evidence for the existence of a single enzyme catalyzing the phosphorylation of choline and ethanolamine in primate lung.

Choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) has been isolated and purified 1000-fold from adult African Green monkey lung with a yield of 10%. The purified enzyme also phosphorylated ethanolamine (ratio of ethanolamine kinase to choline kinase = 0.30). This ratio remained constant throughout the purification procedure. The Km for choline (3.0 - 10(-5) M) was lower than that of ethanolamine (1.2 - 10(-3) M.) Choline was also found to inhibit ethanolamine kinase activity by 50% at a concentration of 0.005 mM, while ethanolamine inhibited choline only at very high concentrations (100--150 mM). When the enzyme was subjected to inactivation by heat, hemicholinium-3, trypsin digestion, and p-hydroxymercuribenzoate, both ethanolamine kinase and choline kinase activities were destroyed at the same rate. Freezing and thawing in the absence of glycerol also destroyed both activities at the same rate. Based on these findings, we conclude that in adult African Green monkey lung tissue, there is only one enzyme for the phosphorylation of ethanolamine and choline, and that choline phosphorylation predominates.