Further condensation of an isopentenyl pyrophosphate (IPPP) with geranyl pyrophosphate (GPP) to form farnesyl pyrophosphate (FAPP) is catalyzed by the prenyltransferases FPP synthase and GGPP synthase (Kavanagh et al, 2006).
The family of enzymes called prenyltransferases is involved in the biosynthesis of isoprenoids. Two members of this family are known to catalyse the sequential condensation of isopentenyl pyrophosphate (IPPP) to DMAPP: farnesyl pyrophosphate synthase dimer (FPPS dimer) and geranylgeranyl pyrophosphate synthetase hexamer (GGPPS hexamer) (Kavanaugh et al, 2006). Both enzymes utlise Mg2+ as cofactor (Chang et al. 2021).
The GGPS1 gene is transcribed to yield mRNA and the mRNA is translated to yield protein. SREBF1A (SREBP1A) and SREBF2 (SREBP2) bind the promoter of the Geranylgeranyl pyrophosphate synthase gene (GGPS1) and enhance transcription (Sakakura et al. 2001, Reed et al. 2008, reviewed in Horton et al. 2002)