siroheme biosynthesis UPa:UPA00262 KEGG:map01110 KEGG:map01100 KEGG:map00860 Biosynthesis of siroheme, the cofactor for sulfite and nitrite reductases. Siroheme is formed by methylation, oxidation, and iron insertion into the tetrapyrrole uroporphyrinogen III (Uro-III). sirohaem biosynthesis PMID:12408752 GO:0019354 PMID:14595395 pathway PMID:11114933 cofactor biosynthesis porphyrin-containing compound metabolism porphyrin-containing compound biosynthesis