Plays a key role in phospholipid biosynthesis by catalyzing the phosphorylation of free choline to phosphocholine, the first step in phosphatidylcholine biosynthesis. Also phosphorylates ethanolamine, thereby contributing to phosphatidylethanolamine biosynthesis. Has higher activity with choline. May contribute to tumor cell growth. This isoform plays a key role in lipolysis of lipid droplets following glucose deprivation (By similarity). In response to glucose deprivation, phosphorylated by AMPK, promoting localization to lipid droplets (By similarity). Phosphorylation is followed by acetylation by KAT5, leading to dissociation of the homodimer into a monomer (By similarity). Monomeric CHKA isoform 1 is converted into a tyrosine-protein kinase, which phosphorylates lipid droplet structural proteins PLIN2 and PLIN3, leading to lipolysis of lipid droplets (By similarity). ATP + choline = ADP + H(+) + phosphocholine ATP + ethanolamine = ADP + H(+) + phosphoethanolamine ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphocholine from choline: step 1/1. Phospholipid metabolism; phosphatidylethanolamine biosynthesis; phosphatidylethanolamine from ethanolamine: step 1/3. Heterodimer with CHKB (By similarity). Homodimer (By similarity). Monomer; acetylation by KAT5 promotes dissociation of the homodimer and monomerization. Isoform 1 localizes to lipid droplets following phosphorylation by AMPK. Testis, brain, lung, kidney and liver. Phosphorylated at Ser-275 by AMPK in response to glucose deprivation, leading to localization to lipid droplets. Acetylated by KAT5 at Lys-243 following phosphorylation by AMPK, leading to monomerization and conversion into a tyrosine-protein kinase. Belongs to the choline/ethanolamine kinase family.