Heterotetrameric enzyme that catalyzes the condensation of farnesyl diphosphate (FPP), which acts as a primer, and isopentenyl diphosphate (IPP) to produce prenyl diphosphates of varying chain lengths and participates in the determination of the side chain of ubiquinone (PubMed:16262699). Supplies nona and decaprenyl diphosphate, the precursors for the side chain of the isoprenoid quinones ubiquinone-9 (Q9) and ubiquinone-10 (Q10) respectively (PubMed:16262699). The enzyme adds isopentenyl diphosphate molecules sequentially to farnesyl diphosphate with trans stereochemistry (PubMed:16262699). May play a role during cerebellar development (PubMed:21871565). May regulate mitochondrial respiratory chain function (PubMed:18437205). (2E,6E)-farnesyl diphosphate + 7 isopentenyl diphosphate = all-trans-decaprenyl diphosphate + 7 diphosphate (2E,6E)-farnesyl diphosphate + 6 isopentenyl diphosphate = all-trans-nonaprenyl diphosphate + 6 diphosphate Cofactor biosynthesis; ubiquinone biosynthesis. Heterotetramer composed of 2 PDSS1/DPS1 and 2 PDSS2/DLP1 subunits. Homozygous mice for PDSS2 are embryonic lethal (PubMed:18437205, PubMed:21871565). The oldest PDSS2 embryo identified is at E9.5, and its morphology resembles normal E6.5 mouse embryo, so the development of mutant embryo may be blocked at late gastrula stage (PubMed:18437205, PubMed:21871565). Conditional knockout mice lacking PDSS2 in cerebellum show severe cerebellum hypoplasia during cerebellum development, whereas conditional knockout mice lacking PDSS2 in Purkinje cells at postnatal stages leads to the development of cerebellar ataxia (PubMed:21871565). Conditional knockout mice lacking PDSS2 in glomeruli show interstitial nephritis characterized by greatly dilated tubules and extensive interstitial infiltration associated with hypercholesterolemia (PubMed:18437205). Liver-conditional knockout mice have no overt disease but their livers have undetectable COQ9 levels, impaired respiratory capacity, and significantly altered intermediary metabolism (PubMed:18437205). Belongs to the FPP/GGPP synthase family.