EC 2.7.7.60     
Accepted name: 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase
Reaction: CTP + 2-C-methyl-D-erythritol 4-phosphate = diphosphate + 4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol
Other name(s): MEP cytidylyltransferase
Systematic name: CTP:2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase
Comments: The enzyme from Escherichia coli requires Mg2+ or Mn2+. ATP or UTP can replace CTP, but both are less effective. GTP and TTP are not substrates. Forms part of an alternative nonmevalonate pathway for terpenoid biosynthesis (for diagram, click here).
References:
1.  Rohdich, F., Wungsintaweekul, J., Fellermeier, M., Sagner, S., Herz, S., Kis, K., Eisenreich, W., Bacher, A. and Zenk, M.H. Cytidine 5′-triphosphate-dependent biosynthesis of isoprenoids: YgbP protein of Escherichia coli catalyzes the formation of 4-diphosphocytidyl-2-C-methyl-D-erithritol. Proc. Natl. Acad. Sci. USA 96 (1999) 11758–11763. [PMID: 10518523]
2.  Kuzuyama, T., Takagi, M., Kaneda, K., Dairi, T. and Seto, H. Formation of 4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol from 2-C-methyl-D-erythritol 4-phosphate by 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase, a new enzyme in the nonmevalonate pathway. Tetrahedron Lett. 41 (2000) 703–706.
[EC 2.7.7.60 created 2001]