Restricted electron flux increases coenzyme Q_(10) production in Agrobacterium tumefaciens ATCC4452

摘要

Coenzyme Q_(10) (CoQ_(10)) is an electron carrier in the respiration chain with antioxidant activity. The effects of aeration and agitation rates, dissolved oxygen levels, an electron flux inhibitor (azide), a proton gradient releaser (2,4-dinitrophenol (DNP)), and an oxidative stressor (hydrogen peroxide (H_2O_2)) on the intracellular CoQ_(10) contents in Agrobacterium tumefaciens ATCC4452 were investigated. With a decrease of dissolved oxygen level from 20 to 5%, the intracellular CoQ_(10) content increased about four-fold, yielding 2 mg/g dry cell weight at 5% dissolved oxygen level. Azide significantly increased the intracellular CoQ_(10) content, with the highest value of 5.3 mg/g dry cell weight in the presence of 0.45 mM of sodium azide. However, DNP (up to 200 μM) and H_2O_2 (up to 10 μM) did not affect the intracellular CoQ_(10) content, indicating proton gradient release, and oxidative stress do not affect the synthesis of CoQ_(10). These results show that restricted electron flux by limited oxygen supply and the addition of azide increases the intracellular CoQ_(10) content, suggesting a feedback regulation of CoQ_(10) biosynthesis by its physiological function of electron carrier in the respiration chain.