The biosynthesis of porphyrins from porphobilinogen by Rhodopseudomonas spheroides

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Abstract
Frozen and thawed cells of R. spheroides, but not whole cells, convert'' porphobilinogen into uroporphyrin and coproporphyrin. Acetone-dried powders of whole cells are stable when stored at -15[degree]C and are the most active source of a coproporphyrin Ill-forming system. The presence of a heat-stable cofactor necessary for coproporphyrin formation was demonstrated. A uroporphyrin I-forming system has been separated, by freezing and thawing, from a uroporphyrin Ill-forming system without the destruction of the latter. Stable acetone-dried powders of these 2 systems were prepared. The effects of change of pH, time of incubation and concentration of enzymes have been studied both with frozen and thawed cells and acetone-dried powders. Neither uroporphyrin I nor uroporphyrin III is converted into coproporphyrin, either by frozen and thawed cells or by acetone-dried powders. Cell-free extracts were made by grinding with alumina. These extracts have weak and unstable coproporphyrin-forming activity.