Factor F,,, is a nickel-containing porphinoid present in methanogenic bacteria. The synthesis of this nickel tetrapyrrole from 5-aminolevulinic acid was studied in Mrthanobuctcrium thermoautotrophicum. This anaerobic archaebacterium was found to accumulate [14C]uroporphyrinogeii 111 (1.8 pmol/g) when growing on nickel-free medium (< 50 nmol/l) supplemented with 2 mM 5-amin0-['~C]Ievulinic acid. The accumulated urophorphyrinogen I11 was quantitatively converted to factor F,,, when the cells were incubated in aminolevulinate-free medium with 5 pM NiCl,. The newly synthesized factor had the same specific radioactivity as the precursor uroporphyrinogen 111. These findings indicate that the nickelporphinoid is biosynthetically derived from uroporphyrinogen 111. The presence and some properties of the enzymes catalyzing the synthesis of uroporphyrinogen I11 from 5-aminolevulinic acid in M . thermoautotrophicum are also described.
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