%0 Journal Article %A Nagata, Kumiko %A Tsukita, Sakura %A Tamura, Toshihide %A Sone, Nobuhito %T A db-type cytochrome-c oxidase terminates the respiratory chain in Helicobacter pylori %D 1996 %J Microbiology, %V 142 %N 7 %P 1757-1763 %@ 1465-2080 %R https://doi.org/10.1099/13500872-142-7-1757 %K microaerobic respiration %K cytochrome-c oxidase %K Helicobacter pylori %I Microbiology Society, %X A Helicobacter pylori membrane fraction oxidized yeast and equine cytochrome c, and N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD). When ascorbate was used as reductant, the V max and apparent K m values were 612 nmol electron min-1 (mg protein)-1 and 14 μM for yeast, and 419 nmol electron min-1 (mg protein)-1 and 19 μM for equine cytochrome c, respectively. For TMPD oxidation, the V max and K m values were 640 nmol electron min-1 (mg protein)-1 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 b- or c-type cytochromes but not aa 3-type cytochromes. c-type and a part of some b-type cytochromes were reduced with ascorbate plus TMPD. A CO difference spectrum revealed that protohaem, but not an aa 3-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 c after SDS-PAGE of the membrane. From these results, it was suggested that the cbb 3-type cytochrome-c oxidase, having a haem-copper binuclear centre like the cytochrome aa 3-type oxidase, but differing in a few other properties, functions as a terminal oxidase in the respiratory chain of H. pylori. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/13500872-142-7-1757