Ubiquinone synthesis by Pneumocystis carinii: Incorporation of radiolabeled polyprenyl chain and benzoquinone ring precursors

Radiolabeled mevalonic acid was incorporated in vitro into Pneumocystis carinii ubiquinone homologs, CoQ₉ and CoQ₁₀, demonstrating the isoprenoid branch pathway forming the polyprenyl chain of ubiquinone is functional in the organism. Radiolabeled shikimic acid, tyrosine and p-hydroxybenzoic acid were also incorporated into the two ubiquinone homologs, indicating that P. carinii also possessed the biochemical pathway for de novo synthesis of the CoQ benzoquinone ring.