TAILIEUCHUNG - Báo cáo khoa học: NADH oxidation and NAD+ reduction catalysed by tightly coupled inside-out vesicles from Paracoccus denitrificans

Tightly coupled inside-out vesicles were prepared from Paracoccus denitrificanscells (SPP, sub-Paracoccusparticles) and characterized kinetically. The rate of NADHoxidation, catalysed by SPP, increases 6–8 times on addition of gram-icidin. The vesicles are capable of catalysing DlH + -dependent reverse electron transfer fromquinol toNAD + . The kinetic parameters of the NADH-oxidase and the reverse electron transfer carried out by membrane-bound P. denitrificanscomplex I were estimated and compared with those of the mitochondrial enzyme. . | Eur. J. Biochem. 269 4020-4024 2002 FEBS 2002 doi NADH oxidation and NAD reduction catalysed by tightly coupled inside-out vesicles from Paracoccus denitrificans Alexander B. Kotlyar and Natalia Borovok Department of Biochemistry George S. Wise Faculty of Life Sciences Tel Aviv University Ramat Aviv Israel Tightly coupled inside-out vesicles were prepared from Paracoccus denitrificans cells SPP sub-Paracoccus particles and characterized kinetically. The rate of NADH oxidation catalysed by SPP increases 6-8 times on addition of gramicidin. The vesicles are capable of catalysing AliH -dependent reverse electron transfer from quinol to NAD . The kinetic parameters of the NADH-oxidase and the reverse electron transfer carried out by membrane-bound P. denitrificans complex I were estimated and compared with those of the mitochondrial enzyme. The data demonstrate that catalytic properties of the dinucleotide-binding site of the bacterial and mitochondrial complex I are almost identical pointing out similar organization of the site in mammals and P. denitrificans. Inhibition of the bacterial complex I by a specific inhibitor of Q reduction rotenone is very different from that of the mitochondrial enzyme. The inhibitor is capable of suppressing the NADH oxidation reaction only at micromolar concentrations while the activity of mitochondrial enzyme is suppressed by nanomolar concentrations of rotenone. In contrast to the mitochondrial enzyme rotenone even at concentrations as high as 10 M does not inhibit the reverse AiH -dependent NAD -reductase reaction on SPP. Keywords NADH Q oxidoreductase complex I reverse electron transfer Paracoccus denitrificans rotenone. NADH-ubiquinone reductase EC commonly known as complex I catalyzes electron transfer from NADH to ubiquinone and couples this process to proton translocation across the inner mitochondrial membrane. The isolated mitochondrial enzyme is composed of more than 40 individual .

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