The two terminal oxidases of the aerobic respiratory chain of Escherichia coli each yield water and not peroxide as a final product.
The aerobic respiratory chain of Escherichia coli contains two terminal oxidases, the cytochrome d complex and the cytochrome o complex. Each of these enzymes catalyzes the oxidation of ubiquinol-8 within the cytoplasmic membrane and reduces molecular oxygen. The purpose of this work is to experimentally verify that each of the terminal oxidases yields water as a product with no significant amount of hydrogen peroxide. This was accomplished by preparing membranes which were washed so as to eliminate membrane-associated catalase and peroxidase activities. The NADH oxidase activity of the membrane-bound respiratory chain was measured by monitoring the rates of both NADH and oxygen utilization. This was performed using membranes from strains in which either cytochrome o or cytochrome d were absent. Results using each strain showed two NADH utilized per oxygen, indicating a four-electron reduction of oxygen to water.
Minghetti
K C
KC
Department of Biochemistry, University of Illinois, Urbana 61801.
Gennis
R B
RB
D000332:Aerobiosis; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D003573:Cytochrome b Group; D017937:Cytochrome d Group; D003580:Cytochromes / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D029968:Escherichia coli Proteins; D010101:Oxygen Consumption; D010545:Peroxides / Q000378:metabolism*; D013045:Species Specificity; D014867:Water / Q000378:metabolism*
D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D010545:Peroxides; D014867:Water; D017937:Cytochrome d Group; C017168:cytochrome bo, E coli