Cytidylyltransferase IspD/TarI (IPR034683)

Short name: IspD/TarI

Overlapping homologous superfamilies

Family relationships


This family consists of cytidylyltransferases IspD and TarI.

2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (IspD) catalyses the formation of 4-diphosphocytidyl-2-C-methyl-D-erythritol from CTP and 2-C-methyl-D-erythritol 4-phosphate (MEP) in the deoxyxylulose pathway of isopentenyl diphosphate (IPP) biosynthesis [PMID: 10841550]. This mevalonate independent pathway that utilizes pyruvate and glyceraldehydes 3-phosphate as starting materials for production of IPP occurs in a variety of bacteria, archaea and plant cells, but is absent in mammals. The isoprenoid pathway is a well known target for anti-infective drug development [PMID: 17081012, PMID: 17921290]. In about twenty percent of bacterial genomes, this protein occurs as IspDF, a bifunctional fusion protein.

Ribitol-5-phosphate cytidylyltransferase (TarI) is required for the synthesis of activated ribitol via the wall teichoic acid biosynthesis pathway. The enzyme catalyzes the transfer of the cytidylyl group of CTP to D-ribitol 5-phosphate to form CDP-ribitol [PMID: 19074383].

The human IspD (known as D-ribitol-5-phosphate cytidylyltransferase or isoprenoid synthase domain-containing protein) shows a canonical N-terminal cytidyltransferase domain linked to a C-terminal domain that is absent in cytidyltransferase homologues. It has cytidyltransferase activity toward pentose phosphates, including ribulose 5-phosphate, ribose 5-phosphate, and ribitol 5-phosphate. It has benn implicated in dystroglycan O-mannosylation [PMID: 26687144, PMID: 27194101].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0070567 cytidylyltransferase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.