EC 2.5.1.89     
Accepted name: tritrans,polycis-undecaprenyl diphosphate synthase [geranylgeranyl-diphosphate specific]
Reaction: geranylgeranyl diphosphate + 7 isopentenyl diphosphate = 7 diphosphate + tritrans,heptacis-undecaprenyl diphosphate
Systematic name: geranylgeranyl-diphosphate:isopentenyl-diphosphate cistransferase (adding 7 isopentenyl units)
Comments: This enzyme is involved in the biosynthesis of the glycosyl carrier lipid in some archaebacteria. Unlike EC 2.5.1.31, its counterpart in most bacteria, it prefers geranylgeranyl diphosphate to farnesyl diphosphate as the allylic substrate, resulting in production of a tritrans,polycis variant of undecaprenyl diphosphate [1].
References:
1.  Hemmi, H., Yamashita, S., Shimoyama, T., Nakayama, T. and Nishino, T. Cloning, expression, and characterization of cis-polyprenyl diphosphate synthase from the thermoacidophilic archaeon Sulfolobus acidocaldarius. J. Bacteriol. 183 (2001) 401–404. [PMID: 11114943]
[EC 2.5.1.89 created 2010, modified 2011]