δ-Aminolevulinic acid dehydratase (δ-aminolevulinic acid hydrolyase EC 4.2.1.24) which catalyzes the formation ofporphobilinogen from two molecules of δ-aminolevulinic acid (ALA) was purified from Chlorella regularis 737-fold by acetone and ammonium sulfate fractionations, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration. The enzyme had an optimum pH of 8.5 in Tris-HCl buffer and required either Mg2+ or Mn2+ for its maximum activity. The Km values for Mg2+, Mn2+ and ALA were 15 μM, 10μM, and 0.5 mM, respectively. The enzyme was not activated by thiol compounds, but was inhibited by p-chloromercuribenzoate. The molecular weight estimated by gel filtration was 316,000 and the isoelectric point was 5.25.
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Tamai et al. (1979) studied this question.