Benzene-induced oxygen consumption by NDO in the presence of hydrogen peroxide-scavenging agents. Additions of benzene (Benz; final concentration, 0.1 mM) and catalase (1,000 U) were made at the times indicated by upward arrows. The reaction mixtures contained the same amounts of NADH and NDO components in 50 mM MES (pH 6.8) as described in Fig. 2. No addition (A) or addition of 0.1 mM FeCl3 · 6H2O (B), 1 mM DETAPAC (C), 1 mM EDTA (D), 10 mM KI and lactoperoxidase (9 U) (E), catalase (1,000 U) (F), and 0.1 mM Fe(NH4)2(SO4)2 · 6H2O (G).