STUDY OF THE TERMINAL PART OF THE RESPIRATORY-CHAIN FROM THE ALKALOTOLERANT BACTERIUM BACILLUS FTU AT DIFFERENT PHASES OF GROWTH

The terminal part of the Bacillus FTU respiratory chain was studied Da ta of difference spectroscopy and the biphasicity of the cyanide titra tion curve of respiration indicate the presence of two types of termin al oxidases (aa(3)-and o-type) in Bac. FTU membranes. The aa(3)-type o xidase was found to dominate at the beginning of the logarithmic growt h phase, while the o-type oxidase was predominant at the stationary gr owth phase. Both enzymes were shown to oxidize TMPD in the presence of ascorbate: the K-m values were 0.7 and 2 mM, and V-max values were 2. 2 mu moles O-2/min per nmole heme o and 11.2 mu moles O-2/min per nmol e heme a for the o-type and aa(3)-type oxidases, respectively. The act ivities of the oxidases were inhibited by KCN to different extents: th e K-i values were 2 and 20 mu M for the aa(3)- and o-type oxidases, re spectively.