Reaction: 2 geranylgeranyl diphosphate + NADPH + H+ = lycopaoctaene + 2 diphosphate + NADP+ (overall reaction)
(1a) 2 geranylgeranyl diphosphate = diphosphate + prephytoene diphosphate
(1b) prephytoene diphosphate + NADPH + H+ = lycopaoctaene + diphosphate + NADP+
For diagram of reaction click here
Glossary: lycopaoctaene = 15,15'-dihydrophytoene = (6E,10E,14E,18E,22E,26E)-2,6,10,14,19,23,27,31-octamethyldotriaconta-2,6,10,14,18,22,26,30-octaene
Other name(s): LOS (gene name)
Systematic name: geranylgeranyl-diphosphate:geranylgeranyl-diphosphate geranylgeranyltransferase
Comments: The enzyme, characterized from the green microalga Botryococcus braunii race L, in involved in biosynthesis of (14E,18E)-lycopadiene. In vitro, the enzyme can accept (2E,6E)-farnesyl diphosphate and phytyl diphosphate as substrates, and is also able to catalyse the condensation of two different substrate molecules, forming chimeric products. However, the use of these alternative substrates is not significant in vivo.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Thapa, H.R., Naik, M.T., Okada, S., Takada, K., Molnar, I., Xu, Y. and Devarenne, T.P. A squalene synthase-like enzyme initiates production of tetraterpenoid hydrocarbons in Botryococcus braunii Race L. Nat Commun 7 (2016) 11198. [PMID: 27050299]
2. Thapa, H.R., Tang, S., Sacchettini, J.C. and Devarenne, T.P. Tetraterpene synthase substrate and product specificity in the green microalga Botryococcus braunii Race L. ACS Chem. Biol. 12 (2017) 2408-2416. [PMID: 28813599]