A membrane fraction oxidized yeast and equine cytochrome and N,N,N’,N’-tetramethyl--phenylenediamine (TMPD). When ascorbate was used as reductant, the and apparent values were 612 nmol electron min (mg protein) and 14 μM for yeast, and 419 nmol electron min (mg protein) and 19 μM for equine cytochrome respectively. For TMPD oxidation, the and values were 640 nmol electron min (mg protein) and 182 μM, respectively. These oxidase activities showed a high affinity for oxygen. Inhibition of both cytochrome-c and TMPD oxidase activities by 50% was caused by about 4 μM cyanide and about 0.5 mM azide. Redox difference spectra of the membrane solubilized with Triton X-100 showed - or -type cytochromes but not -type cytochromes. -type and a part of some -type cytochromes were reduced with ascorbate plus TMPD. A CO difference spectrum revealed that protohaem, but not an -type cytochrome, may be interacting with CO/oxygen. Only protohaem was detected in the haem fraction extracted from the membrane. Three polypeptides (60, 38 and 29 kDa) were found to be bearing haem after SDS-PAGE of the membrane. From these results, it was suggested that the -type cytochrome- oxidase, having a haem-copper binuclear centre like the cytochrome -type oxidase, but differing in a few other properties, functions as a terminal oxidase in the respiratory chain of


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error