Anti-phosphate cytidylyltransferase 1B, choline antibodies are used for the immunodetection of the protein encoded by the PCYT1B gene. In humans, the canonical protein has a reported length of 369 amino acid residues and a mass of 41.9 kDa. Its subcellular localization is in the ER and cytoplasm. Alternative splicing is reported to yield 4 different isoforms for this protein. A member of the Cytidylyltransferase protein family, it is known to catalyze the key rate-limiting step in the CDP-choline pathway for phosphatidylcholine biosynthesis. Post-translational modifications have been described, including phosphorylation. Other names for this target antigen include CTB, CCT B, CCT-beta, CT B, and CCTB. Gene orthologs have been identified in the mouse, rat, bovine, frog, chimpanzee and chicken species.