Figure 3. Heat sensitivity of LUPOs from Lepidium. (A) Peroxidases from Lepidium dissolved in a phosphate buffer of low [Ca²⁺] were treated with the temperatures indicated before the light yield of the H₂O₂-luminol reaction was measured. The temperature of 50% inactivation (ET₅₀ = 36.7°C) is the curve's point of inflexion. (B) Data from A are plotted on a log scale to show that the ET₅₀ is identical to the point of maximal curve bending. Data given are means of n = 5. Data are taken from.³¹ (C) The same experiment was performed as described in A, however this time peroxidases were kept in TriCaT-buffer (high [Ca²⁺]) during heat treatment. The temperature of 50% inactivation is 57.4°C. Means of n = 3 individual measurements are shown. (D) Data from C plotted on a log scale. Luminescence is expressed relative to luminescence from samples kept at RT (≈20°C). R² are correlation coefficients obtained from curve fitting. Error bars represent StDv or are below symbol size.