Ethanolamine kinase from Culex pipiens fatigans

Abstract Ethanolamine kinase was partially purified from the larvae of Culex pipiens fatigans and its properties were studied. The enzyme was separated from choline kinase by acetic acid precipitation at pH 5.0 of a 13,000 g supernatant of the larval homogenate. Alkaline phosphatase activity was removed from the enzyme preparation by the acid treatment followed by ammonium sulfate fractionation. The enzyme was localized in the cytosolic fraction and had a requirement for Mg 2+ as a cofactor. The K m values for ethanolamine and ATP were 4 × 10 −4 and 1.54 × 10 −4 m , respectively. The affinity of the enzyme for nucleotide triphosphates was in the order, ATP > ITP > GTP while UTP and CTP were poorly utilized. p -Chloromercuribenzoate and N -ethylmaleimide inhibited the enzyme activity and reduced glutathione protected the enzyme from their inhibition. Choline and serine had no effect on the enzyme activity. The enzyme had a molecular weight of 44, 000 daltons as determined by gel filtration chromatography. Eggs contained the highest specific activity of the enzyme while adult insects had the highest total enzyme activity.