Cytidylyltransferase <p>This family includes [<cite idref="PUB00000266"/>]:</p><ul> <li>Cholinephosphate cytidyltransferase (<db_xref db="SWISSPROT" dbkey="P49585"/>).</li><li>Glycerol-3-phosphate cytidyltransferase (<db_xref db="SWISSPROT" dbkey="P27623"/>).</li> </ul><p>CTP:cholinephosphate cytidylyltransferase (CCT) is a key regulatory enzyme in phosphatidylcholine biosynthesis that catalyzes the formation of CDP-choline. A comparison of the catalytic domains of CCTs from a wide variety of organisms reveals a large number of completely conserved residues. There may be a role for the conserved HXGH sequence in catalysis. The membrane-binding domain in rat CCT has been defined, and it has been suggested that lipids may play a role in inactivating the enzyme. A phosphorylation domain has been described [<cite idref="PUB00006392"/>].</p>