in addition to the phosphorylation of choline, ck has also been shown to phosphorylate ethanolamine, a precursor to another important glycerophospholipid, phosphatidylethanolamine. ck functions as a dimer consisting of either α1, α2 or β subunits. each ck isoform is ubiquitously expressed throughout tissues, however ckα is enriched in the testis and liver, whereas ckβ is enriched in the liver and the heart. homozygous deletion of ckα is embryonic lethal after about 5 days, whereas deletion of ckβ is not.