This reaction involves the transfer of a phosphate group from adenosine triphosphate (ATP) to choline in order to form phosphocholine.
Thus, the two substrates of this enzyme are ATP and choline, whereas its two products are adenosine diphosphate (ADP) and O-phosphocholine.
These isoforms are encoded by two separate genes, CHKA and CHKB and are only active in their homodimeric, heterodimeric and oligomeric forms.
Only residues that are involved in direct salt bridges, hydrogen bonds, or van der Waals interactions are shown.
Since the structure of CK is very similar to that of the eukaryotic protein kinase family, the location of ATP and choline binding pockets have been proposed.
[citation needed] Propositions for this mechanism have been made based on mechanistic studies done on eukaryotic protein kinases.
It has been proposed that in the CKα-2 mechanism, ATP binds first, followed by choline, and then the transfer of the phosphoryl group takes place.
Phosphatidylcholine is important for a variety of function in eukaryotes such as facilitating the transport of cholesterol through the organism, acting as a substrate for the production of second messengers and as a cofactor for the activity of several membrane-related enzymes.
[9] CK also plays a vital role in the production of sphingomyelin, another important membrane phospholipid and in the regulation of cell growth.
It has also been found that CK plays a critical role in the proliferation of human mammary epithelial cells.
[13] ShRNA mediated in vivo depletion of CKα has been shown to decrease the growth of prostate tumor xenografts[12] Overexpression of CKα-1 has been found to be associated with cancer.
This suggests that defect in CKβ may lead to a decrease in PC synthesis in the muscles resulting in muscular dystrophy.