[122] Porphyrin synthesis

Publisher Summary This chapter focuses on porphyrin synthesis; and describes the assay method, purification procedure, and properties of uroporphyrinogen I synthetase, uroporphyrinogen III cosynthetase, and uroporphyrinogen decarboxylase. A complete assay for uroporphyrinogen I synthetase (UI-S) includes determinations of reaction rate, yield of uroporphyrinogen (Urogen), and isomer number of the product. In the assay of uroporphyrinogen III cosynthetase, reaction is catalyzed by UI-S and uroporphyrinogen III cosynthetase (UIII-coS) when incubated together. The rate of PBG consumption is related to the concentration of UI-S; thus PBG disappearance cannot be used as an assay for UIII-coS. And, in the assay of uroporphyrinogen dccarboxylase, the rate of conversion of Urogen to Coprogen is measured. After oxidation of these porphyrinogens to porphyrins they can be separated from one another by partition between an aqueous and an ether phase. The uroporphyrins are not soluble in ether, whereas the coproporphyrins are extracted from an aqueous phase at pH 3.5 into ether. The concentration of Copro is determined spectrophotometrically.