Ubiquinone biosynthesis O-methyltransferase, mitochondrial (COQ3)

Ubiquinone biosynthesis O-methyltransferase, mitochondrial (COQ3) is a nuclear-encoded mitochondrial enzyme that catalyzes two O-methylation steps in the biosynthesis of ubiquinone (coenzyme Q)[1][4][5][13]. Ubiquinone is a lipid-soluble electron carrier essential for the mitochondrial electron transport chain, and hence for ATP production in eukaryotes and prokaryotes. COQ3 specifically methylates key biosynthetic intermediates, including 3,4-dihydroxy-5-polyprenylbenzoic acid and demethyl-ubiquinone, toward production of functional coenzyme Q[1][4][5]. The enzyme is part of the multi-protein “COQ metabolon” or “CoQ synthome”, a complex required for coordinated ubiquinone production[2][3]. Mutations in COQ3 can lead to primary coenzyme Q10 deficiency, which manifests in various mitochondrial disease phenotypes, including optic atrophy and encephalopathy[4][1]. There is currently no direct pharmacological targeting of COQ3; clinical management may involve coenzyme Q10 supplementation to circumvent biosynthetic defects[4]. Key details are directly supported by genomic, protein, and biochemical resources, including OMIM, GeneCards, UniProt, and primary literature[1][4][5][13].

Other names

Coenzyme Q3, methyltransferase3-demethylubiquinol 3-O-methyltransferase3-demethylubiquinone 3-O-methyltransferasePolyprenyldihydroxybenzoate methyltransferaseDHHB methyltransferaseDHHBMTDHHBMTASE2-polyprenyl-6-hydroxyphenol methylase3,4-dihydroxy-5-hexaprenylbenzoate methyltransferaseCoQ3 homolog, methyltransferaseHexaprenyldihydroxybenzoate methyltransferaseUG0215E05BA9819.1

Not directly drug-targeted; supplemental CoQ10 acts as a biochemical bypass, not by direct inhibition or activation of COQ3.