GGPPS

GGPPS stands for geranylgeranyl pyrophosphate synthase, an enzyme in the isoprenoid biosynthesis pathway that catalyzes the formation of geranylgeranyl pyrophosphate (GGPP), a key 20-carbon donor used to build a wide range of biological isoprenoids. Most GGPP synthases operate by condensing isopentenyl pyrophosphate (IPP) with an allylic substrate such as dimethylallyl pyrophosphate (DMAPP) or farnesyl pyrophosphate (FPP), yielding GGPP through one or more condensation steps.

In bacteria and many non-plant organisms, GGPPS is typically a single-subunit enzyme located in the cytosol. In plants and some algae, GPPS activity can be provided by heteromeric complexes composed of a large subunit and a small subunit, which together regulate the production and chain length of the product. In plastids, these enzymes supply GGPP for plastidial isoprenoids, while in other cellular compartments GGPP serves as a substrate for various biosynthetic pathways.

GGPP is a crucial precursor for multiple classes of isoprenoids, including carotenoids, chlorophylls, tocopherols (vitamin E), ubiquinone (coenzyme Q), and dolichols. It also serves as the lipid anchor for the geranylgeranylation of certain proteins, a post-translational modification performed by geranylgeranyltransferases that is important for membrane association and function of small GTPases and other signaling proteins.

In humans, GGPS genes (including GGPS1) encode GGPP synthase isoforms; in plants, gene families and subunit composition contribute to developmental regulation and pigment production. GGPPS is a target of metabolic engineering to alter isoprenoid flux and to study protein prenylation-dependent processes.