Effect of Oxygen on Several Enzymes Involved in the Aerobic and Anaerobic Utilization of Glucose in Escherichia coli

Abstract

By using the continuous culture technique, the transition from aerobiosis to anaerobiosis and its effect on a number of enzymes has been investigated in Escherichia coli K-12. A decrease in the oxygen partial pressure below 28.0 mm of Hg resulted firstly in an increase of the respiratory enzymes (reduced nicotinamide adenine dinucleotide [NADH] oxidase, 2.53-fold; succinic dehydrogenase, 1.4-fold; cytochrome b1 3.91-fold; and cytochrome a2, 2.45-fold) before the electron transport system gradually collapsed as cytochrome a2, followed by cytochrome b1 succinic dehydrogenase, and finally NADH oxidase decreased in activity. The change from respiration to fermentation was initiated well before the oxygen tension reached zero by the increase in levels of fructose diphosphate-aldolase, glucose 6-phosphate, and 6-phosphogluconate dehydro-genases and a decrease in 2-oxoglutarate dehydrogenase. When the dissolved oxygen tension reached zero, dry weight and CO2 formation together with isocitrate dehydrogenase decreased, whereas acid production and phosphofruc-tokinase synthesis started to increase. Enzymatic investigations revealed that the kinetics of the enzyme phosphofructokinase from strict aerobic cultures (6.9 ppm oxygen in solution) was adenosine triphosphate (ATP)-insensitive, whereas the same enzyme from anaerobic cultures was ATP-sensitive. A mech-anism is proposed for the change from aerobiosis to anaerobiosis together with the occurring change in glucose regulation.