PDSS2 (decaprenyl diphosphate synthase subunit 2) is a heterotetrameric enzyme catalyzing sequential condensation of farnesyl diphosphate and isopentenyl diphosphate molecules to produce prenyl diphosphate precursors 1. The enzyme specifically supplies nona- and decaprenyl diphosphate, which are essential for synthesizing the isoprenoid side chains of ubiquinone-9 and ubiquinone-10 respectively 1. PDSS2 plays critical roles in mitochondrial bioenergetics, as demonstrated by its role in female reproductive aging, where diminished PDSS2 expression in oocytes causes mitochondrial dysfunction, reduced ATP production, and premature ovarian failure reversible by CoQ10 supplementation 2. Beyond CoQ10 biosynthesis, PDSS2 exhibits non-enzymatic tumor-suppressive functions in lung cancer, where it inhibits cell proliferation and migration independently of catalytic activity 3. Mutations in PDSS2 cause primary coenzyme Q10 deficiency, associated with infantile multisystemic disease and cerebellar ataxia 4. Additionally, PDSS2 expression supports metabolic adaptation in tissue-resident memory T cells, where overexpression enhances mitochondrial respiration and antitumor immunity 5. PDSS2 regulation involves transcription factor Sp1-mediated repression, with downregulated expression correlating with poor prognosis in multiple cancer types.