NATURE OF THE ACTIVATING ENZYME OF THE INACTIVE FORM OF DELTA-AMINOLEVULINATE SYNTHETASE IN RHODOPSEUDOMONAS-SPHEROIDES

The activating enzyme of the inactive form of Fraction I of δ-aminolevulinate (ALA) syn-thetase [EC 2.3.1.37] in Rhodopseudomonas (R.) spheroides was purified about 1,000-fold from an extract of R. spheroides cells grown anaerobically in the light. The purification of the activating enzyme was achieved by fractionating the 100,000 × g supernatant fraction of the crude extract with ammonium sulfate and acetone, followed by Sephadex G-200 chromatog-raphy, pyridoxamine phosphate-Sepharose 4B chromatography, and preparative gel electro-phoresis. The final preparation of the activating enzyme still contained a minor contaminant (less than 20%) as judged by disc gel electrophoresis. The activating enzyme exhibited cys-tathionase [EC 4.4.1.1] activity throughout the purification. These two enzyme activities were not separated at all during any step of the purification. An apparently homogeneous preparation of cystathionase [EC 4.4.1.8] purified from rat liver also exhibited activating activity in the presence of L-cystine. It was concluded that the activating enzyme is a cystathionase. © 1979 by The Journal of Biochemistry.