抄録
A ferrocytochrome c: hydrogen-peroxide oxidoreductase (EC 1. 11. 1. 5) was purified from the obligate chemoautotroph Thiobacillus thiooxidans. The purified enzyme had protoheme as the prosthetic group and its absorption maxima were 397, 489 and 635 nm in oxidized form, while 422 and 560 nm in reduced form. The molecular weight and the sedimentation coefficient were estimated to be 32, 000 and 2.7 S, respectively. The enzyme utilized ferrocytochrome c and NADH as an electron donor. Both peroxidizing activities toward cytochrome c of T. thiooxidans and that of horse heart were almost the same level. The activity of ferrocytochrome c peroxidation increased in almost parallel with that of NADH peroxidation in the course of purification of the enzyme. Both enzyme activities were highly stable at pH 7.0 against heating. The ferrocytochrome c peroxidizing activity was inhibited completely with 1mM cyanide and about 60% with 1mM azide. Although ten-fold higher concentration of inhibitors was required, NADH peroxidizing activity was also inhibited with cyanide and azide. Both peroxidizing activities were inhibited about 60% with CO.
