Reaction: geranylgeranyl diphosphate + homogentisate = diphosphate + 6-geranylgeranyl-2-methylbenzene-1,4-diol + CO2
For diagram of reaction click here.
Glossary: 6-geranylgeranyl-2-methylbenzene-1,4-diol = MGGBQ
Other name(s): HGGT; slr1736 (gene name)
Systematic name: geranylgeranyl-diphosphate:homogentisate geranylgeranyltransferase
Comments: Requires Mg2+ for activity. Involved in the biosynthesis of the vitamin E, tocotrienols. While the enzyme from the bacterium Synechocystis PCC 6803 has higher activity with phytyl diphosphate (EC 2.5.1.115, homogentisate phytyltransferase), the enzymes from barley, rice and wheat have only a low activity with that substrate [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Collakova, E. and DellaPenna, D. Isolation and functional analysis of homogentisate phytyltransferase from Synechocystis sp. PCC 6803 and Arabidopsis. Plant Physiol. 127 (2001) 1113-1124. [PMID: 11706191]
2. Cahoon, E.B., Hall, S.E., Ripp, K.G., Ganzke, T.S., Hitz, W.D. and Coughlan, S.J. Metabolic redesign of vitamin E biosynthesis in plants for tocotrienol production and increased antioxidant content. Nat. Biotechnol. 21 (2003) 1082-1087. [PMID: 12897790]
3. Yang, W., Cahoon, R.E., Hunter, S.C., Zhang, C., Han, J., Borgschulte, T. and Cahoon, E.B. Vitamin E biosynthesis: functional characterization of the monocot homogentisate geranylgeranyl transferase. Plant J. 65 (2011) 206-217. [PMID: 21223386]