On the presence and significance of coenzyme Q in microsomes

Subcellular Distribution of Ubiquinone and the Content of Ubiquinone and Other Electron Carriers in the Mitochondria Isolated from Tobacco Cultured Cells

“…UQ is concentrated in the 250 ~ 1000 x g and 1 000 ~ 10,000 x g particles, and its distribution is well correlated with the distribution of Cyt c oxidase activity in the particles. The relatively high level of UQ compared to Cyt c oxidase activity in the soluble (supernatant) and microsomal fraction (10,000 ~ 100,000 x g pellet) of the cells is consistent with the report by Leonhiiuser et al 25 ) who found UQ in animal tissue microsomes. These fractions could have some mitochondrial fragments, however, as similar results were obtained with spinach leaves by Crane.…”

Requirement for coenzyme Q in plasma membrane electron transport.

“…Coenzyme Q (CoQ, ubiquinone) is present in the endomembranes ofcells (1)(2)(3)(4) as well as in mitochondria, where it serves as a central component of the transmembrane electron transport system (5). The CoQ in endomembranes is concentrated in the Golgi apparatus and plasma membrane (4).…”

Biological Oxidations

“…Although it is clear that extraction of CoQ from mitochondria inhibits the succinate oxidase activity while addition can restore the antimycin and cyanide sensitive activity again in mammalina mitochondria (19) or bacterial particles (20), it is still not clear whether CoQ is on the main electron trans port pathway. The fact that the quinone is present in the nuclear fraction (21) and microsomes (21,22) makes a specific role in electron transport hard to visualise. Furthermore, the fact that the oxidation of NADH by NADH CoQ reductase (23) cannot be mediated by COQlD but only by CoQo and COQ2 makes a role of CoQ in this part of the respiratory chain rather uncer tain.…”