Figure 5: Activity of catalase containing various heme-iron species.

(a) Representative experiment showing the ultraviolet–visible spectral changes monitored at 25 °C when compound II-containing catalase (2.4 μM) obtained under pathological conditions with HCys (200 μM) reacts with NaSH in 50 mM KPi at pH 7.4. (b) Activity of the various species obtained in (a) (n=3±s.d.). Notably, sulf-CAT–Fe(III)-SH2 contains a mixture of native CAT–Fe(III) and sulf-CAT–Fe(III)-sulfide. The activity of CAT–Fe(II)-sulfonium and sulf-CAT–Fe(III) were taken from Fig. 4g.