1987 Volume 35 Issue 4 Pages 1531-1537
Quinones contained in the membrane of Photobacterium phosphoreum grown aerobically were studied. Ubiquinone-8 (Q-8), menaquinone-8 (MK-8), and demethylmenaquinone-8 (DMK-8) were identified by mass spectroscopy. To establish the function of the quinones in the aerobic respiratory chain, depletion and reincorporation experiments were performed. Quinones were removed efficiently by n-pentane-acetone (9 ;1, v/v) extraction. The depleted membrane showed no reduced nicotinamide adenine dinucleotide (NADH) oxidase activity and yet retained NADH dehydrogenase activity and ubiquinol-1 (Q1H2) oxidase activity.
When Q-8 was reincorporated into quinone-depleted membrane vesicles by a freeze-thaw-sonication method, the NADH oxidase activity was restored completely. However, the other quinones contained in P. phosphoreum (MK-8 and DMK-8) did not have the ability to restore the activity of NADH oxidase. The Q1 H2 oxidase or NADH dehydrogenase activity did not alter with the addition of the three kinds of quinones. These results suggest that Q-8 is a component of the aerobic respiratory chain of P. phosphoreum.
