Plays a key role in phospholipid biosynthesis by catalyzing the phosphorylation of free choline to phosphocholine, the first step in phosphatidylcholine biosynthesis (PubMed:19915674, PubMed:34077757, PubMed:17007874). Also phosphorylates ethanolamine, thereby contributing to phosphatidylethanolamine biosynthesis (PubMed:19915674, PubMed:17007874). Has higher activity with choline (PubMed:19915674, PubMed:17007874). May contribute to tumor cell growth (PubMed:19915674). This isoform plays a key role in lipolysis of lipid droplets following glucose deprivation (PubMed:34077757). In response to glucose deprivation, phosphorylated by AMPK, promoting localization to lipid droplets (PubMed:34077757). Phosphorylation is followed by acetylation by KAT5, leading to dissociation of the homodimer into a monomer (PubMed:34077757). 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 (PubMed:34077757). ATP + choline = ADP + H(+) + phosphocholine ATP + ethanolamine = ADP + H(+) + phosphoethanolamine ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Homodimerization or heterodimerization is required for the choline and ethanolamine kinase activities. Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphocholine from choline: step 1/1. Phospholipid metabolism; phosphatidylethanolamine biosynthesis; phosphatidylethanolamine from ethanolamine: step 1/3. Homodimer (PubMed:34077757, PubMed:17007874, PubMed:20299452). Heterodimer with CHKB (By similarity). Monomer; acetylation by KAT5 promotes dissociation of the homodimer and monomerization. (Microbial infection) Interacts with PI4KA/PI4KIIIalpha; CHKA bridges PI4KA/PI4KIIIalpha and hepatitis C virus (HCV) non-structural protein 5A (NS5A) and potentiates NS5A-stimulated PI4KA activity, which then facilitates the targeting of the ternary complex to the ER for viral replication. Isoform 1 localizes to lipid droplets following phosphorylation by AMPK. Phosphorylated at Ser-279 by AMPK in response to glucose deprivation, leading to localization to lipid droplets. Acetylated by KAT5 at Lys-247 following phosphorylation by AMPK, leading to monomerization and conversion into a tyrosine-protein kinase. Belongs to the choline/ethanolamine kinase family.