Purification and Some Properties of Isocitrate Lyase from Paecilomyces varioti with High Malic Acid Production

概要

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Isocitrate lyase was purified 135-fold to a homogeneous state from acetate-grown cells of Paecilomyces varioti, which produces malic acid from non-sugar carbon sources. Addition of dithiothreitol to the buffer systems effectively prevented the loss of enzyme activity during purification. The purified enzyme had a molecular weight of 240,000 and a subunit molecular weight of 60,000. The optimum pH for the reaction was 7.2 and the optimum temperature was 37℃. The enzyme activity was stimulated by Mg^<2+> and Mn^<2+>, though the extent of activation by Mn^<2+> was less than by Mg^<2+>. The effect of some metabolic intermediates on isocitrate lyase was also investigated. The enzyme activity was inhibited competitively by α-ketoglutarate and non-competitively by phosphoenolpyruvate, pyruvate, oxalacetate, and succinate. Malate, fumarate and citrate had no inhibitory effect at the concentration of 0.1 mM. The K_m value for threo Ds(+)-isocitrate was calculated to be 0.018 mM.
社団法人日本生物工学会の論文
1984-12-25