Ubiquinone metabolism

Ubiquinone, also known as coenzyme Q is an integral component of electron transport chain. In electron transport chain of inner mitochondrial membrane, ubiquinone acts as an electron carrier transferring electrons from NADH dehydrogenase (complex I) and succinate dehydrogenase (complex II) to cytochrome bc1 complex (complex III). Ubiquinone is synthesised from chorimsate, end product of shikimate pathway in nine enzyme-catalysed reactions. The other important co-substrates involved in this pathway are glutamine, isoprenoids (terpenoid metabolism) and S-adenosyl methionine (methionine metabolism). This pathway is identical in all apicomplexans including Toxoplasma gondii, Neospora caninum and Plasmodium falciparum and the enzymes missing in the genomes of all these species are oxo-acid lyase and 3-octaprenyl-4-hydroxybenzoate carboxy-lyase.

 

Enzyme EC Number Gene id
FAD-dependent monooxygenase (Ubiquinone biosynthesis monooxygenase) 1.14.13.- NCLIV_032510
UbiB Hydroxylase (2-octaprenylphenol hydroxylase) 1.14.13.- NCLIV_063390
Ubiquinone/menaquinone biosynthesis methyltransferase 2.1.1.- NCLIV_002130
Ubiquinone/menaquinone biosynthesis methyltransferase 2.1.1.- NCLIV_029250
Ubiquinone/menaquinone biosynthesis methyltransferase 2.1.1.- NCLIV_064020
3-demethylubiquinone-9 3-O-methyltransferase 2.1.1.64 NCLIV_039200
3-demethylubiquinone-9 3-O-methyltransferase 2.1.1.64 NCLIV_065110
p-hydroxybenzoate-polyprenyltransferase 2.5.1.- NCLIV_027400
3-octaprenyl-4-hydroxybenzoate carboxy-lyase 4.1.1.- Missing in annotation
Oxo-acid  lyase 4.3.1.- Missing in annotation
Coq4 none NCLIV_007060
ABC1 protein required for ubiquinone biosynthesis none NCLIV_021150

 

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Sources and fates of metabolites

 

Substrate Source pathways Product Fate pathways
Chorismate Shikimate biosynthesis Pyruvate Pyruvate metabolism, Alanine metabolism
Glutamine Glutamate metabolism Glutamate Glutamate metabolism
All-trans-Geranyl-Geranyl-PP Terpenoid metabolism    
S-adenosylmethionine Methionine metabolism S-adenosylhomocysteine Methionine metabolism