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The effects of the iron ions for the light-induced mitochondrial F_0F₁-ATPase of Lentinus edodes was studied. The enzyme activity was stimulated up to 202% by 0.1 mM Fe^(2+) ion, but was inhibited by Fe^(3+) and Mg^(2+). In the presence of 0.5 mM Mg^(2+), the activity also increased 32% by 0.1 mM Fe^(2+) ion, and decreased to a similar extent by Fe^(3+) ion than by only Fe^(3+) ion. Also, the activity was inhibited 53% by 5.0 mM Fe^(2+) ion in the presence of 0.5 mM Mg^(2+) ion and various concentration of Fe^(3+) ion(mM). These results showed that Fe^(2+) strongly stimulated the enzyme activity and its role for the enzyme was independent of Mg^(2+) ion, but was dependent of Fe^(3+) ion. From inactivation of the enzyme by addition of metal chelating agent, EDTA, it is suggested that the enzyme is to be metalloenzyme. The optimal pH and temperature of the enzyme in the presence of 0.1 mM Fe^(2+) was 7.6 and 63℃, respectively.
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