Figure 1.

Scheme of CoQ synthesis in mitochondria. (A) Synthesis of the mevalonate chain in the ER and quinone head processing from tyrosine in cytosol or mitochondrial matrix. (B) Assembly of benzene ring and isoprenoid tail at the inner mitochondrial membrane and further modifications of the phenol head at the inner mitochondrial membrane. Members of the CoQ-synthome are indicated in each step. In some cases, the enzyme involved in some of the steps are unknown. Regulatory enzymes such as COQ8 and COQ9 are indicated at the steps in which they are actively involved.