抄録
δ-Aminolevulinic acid (δ-ALA) synthases from Protaminobacter ruber and Rhodopseudomonas spheroides were highly purified and characterized. The molecular weights of the δ-ALA synthases from P. ruber and R. spheroides were estimated to be 97, 000 and 87, 000, respectively. The optimum pH was about 8.0 for both enzymes. The P. ruber-enzyme showed Kms of 1.05mM for glycine and 0.77μM for pyridoxal-5'-phosphate (PLP), while the R. spheroides-enzyme showed Kms of 8.33mM for glycine and 15μM for PLP. The P. ruber-enzyme was less stable during storage at 4°C or 37°C than the R. spheroides-enzyme. As to the effects of end-products, the P. ruber-enzyme was not inhibited by hemin, while the R. spheroides-enzyme was considerably inhibited by hemin. A higher concentration of vitamin B12 stimulated the reaction of the δ-ALA synthases, especially the P. ruber-enzyme.
