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In order to investigate the antigenic nature of the bovine hepatic δ-aminolevulinate dehydratase (EC 4.2.1.24), the enzyme was purified in its enzyme activity 620 times as potent as the crude enzyme by affinity chromatographic method of Anderson and Desnick(1979). Rabbit antiserum against the purified enzyme was prepared by method of Alexander and kenny(1977). Antigenicity of the enzyme preparation obtained at each purification step was determined by method of Ouchterlony double-gel diffusion, rocket immunoelctrophoresis, and two dimensional immunoelectrophoresis. It was confirmed that there were three antigenic fractions a, b, and c and four non-antigenic fractions d, e, f, and g in the supernatant of bovine liver homogenate. Out of three antigenic fractions, fractions b and c were eliminated by DEAE-cellulose column chromatography, suggesting that these two protein fractions were not enzymatically active even though their antigenicities were identical. Fraction a which was carried over to the final stage of purification through octyl-Sepharose CL-4B, phenyl-Sepharose CL-4B chromatography an Sephadex G-200 gel filtration was considered to be enzymatically active protein fraction. It seemed that the fraction which was consisted of 8 subunits (octamer) was in a state equilibrium with tetramers into which octamers were divided by second Sephadex G-200 gel filtration, their antigenicity being identical. Out of four non-antigenic fractions, fraction d was found until the last step of purification, not being eliminated by second Sephadex G-200 gel filtration.
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