FIGURE 5.

Effects of malonate and atpenin A5 on rates of H₂O₂ production by mitochondria oxidizing glycerol 3-phosphate. a, α/β glycerol 3-phosphate was added at different concentrations in the presence of 4 μm rotenone, 2 μm myxothiazol, and 2 μm antimycin A. Where indicated, malonate was present at 500 μm or atpenin A5 was present at 1 μm. Data are means ± S.E. (n = 3) b, rate of H₂O₂ production during oxidation of 27 mm α/β glycerol 3-phosphate in the presence of 4 μm rotenone, in the absence and presence of 500 μm malonate or 1 μm atpenin A5. Neither malonate nor atpenin A5 change the rate of respiration or the reduction state of the NAD(P)H or cytochrome b pools indicating that these inhibitors do not affect substrate oxidation or the reduction state of other relevant ROS producing redox centers, as described in Ref. 12 (data not shown). Data are means ± S.E. (n = 5–6) c, normalized rates of H₂O₂ production in the forward reaction at 400 μm succinate are shown in the first three bars (data from Fig. 4b). 500 μm malonate or 1 μm atpenin A5 were present where indicated. The final three bars are the normalized rates of H₂O₂ production in the reverse reaction. Data from a at 27 mm glycerol 3-phosphate (G3P) were normalized to the activity of the enzyme incubated under identical conditions (as described for Fig. 4). The rate in the presence of 500 μm malonate was made zero by definition. Data are means ± S.E. (n = 3). *, significantly different from rate without malonate or atpenin A5 (p < 0.02).