Abstract
Coenzyme Q (CoQ, Ubiquinone) is well-known to act as an essential carrier for the electron transfer from flavin proteins to the bc1 complex and concomitant trans-membrane transport of protons in the mitochondrial respiratory chain. However, COQ is found in all intracellular organelles and it appears to be provided by the endoplasmic reticulum-Golgi system as well as mitochondria. These observations suggest that intracellular CoQ may also have important physiological roles besides the mitochondrial respiratory chain. A greater part of CoQ widely distributed in intracellular organelles and serum is present as ubiquinol, the reduced form, and is suggested to act as an endogenous antioxidant. In addition, it is also suggested that COQ may be involved in activation of some uncoupling proteins, mitochondrial permeability transition, apoptosis and so on. This paper focuses on newly revealed physiological roles of CoQ in various biological systems.
