2 TYPES OF TERMINAL OXIDASE IN ALKALOTOLERANT BACILLUS FTU

The terminal segment of the Bacillus FTU respiratory chain has been st udied. The shape of difference spectra and biphasic cyanide titration curve point to the presence of two terminal oxidases (aa3- and o-type) in the subcellular membrane vesicles of this Bacillus. The aa3-type o xidase was shown to dominate in the beginning of the logarithmic phase while the o-type oxidase was more pronounced at the stationary phase of bacterial growth. Both enzymes oxidized TMPD in the presence of asc orbate: the o-type oxidase with K(m) = 0.7 mM TMPD and V(max) = 2.2 mu mol O2 min-1 nmol-1 haem o and the aa3-type oxidase with K(m) = 2 mM T MPD and V(max) = 11.2 mumol O2 min-1 nmol-1 haem a. KCN inhibited the two oxidases (half-maximal inhibition at 2 muM and 20 muM for the aa3- and o-type oxidases, respectively).