Electron transport chain from glycerol 3 phosphate to nitrate in Escherichia coli

Abstract

It is known that in E. coli two dehydrogenases of the flavoprotein kind can participate in the transfer of hydrogens from sn glycerol 3 phosphate (G3P) to nitrate and that possession of either enzyme is sufficient to permit anaerobic growth on glycerol as carbon source and nitrate as hydrogen acceptor. Results from this study show that under such a growth condition a protein with light absorption characteristics of cytochrome b1 is induced. If G3P, nitrate and adenosine diphosphate are added anaerobically to a particulate fraction prepared from these cells, four reactions can be detected: the reduction of the cytochrome b1 like protein, the formation of dihydroxyacetone phosphate (DHAP), the formation of nitrate, and the generation of adenosine 5' triphosphate (ATP). The anaerobic G3P dehydrogenase system can yield an ATP DHAP (or ATP nitrite) molar ratio of about 0.2, whereas the aerobic G3P dehydrogenase system can yield a corresponding ratio of about 0.3. The hydrogen transfer activity is sensitive to respiratory inhibitors such as cyanide, Rotenone, and 2 heptyl 4 hydroxyquinoline N oxide.