[The chemistry of porphyrins and their precursors on the heme biosynthetic chain].

There are two ways for numbering the positions of C and N atoms in the porphyrin ring. The Fisher numeration is relatively old styled, but at present, is most widely employed among chemists because of its simpler and easier technique than that of the IUPAC numeration which is more effective in numbering the complicated structures of recent synthetic chemical including recent porphyrin derivatives. Uroporphyrinogen III, Coproporphyrinogen III and Protoporphynogen IX have been described as the porphyrin intermediates in heme biosynthesis. Uroporphyrins, Coproporphyrins and Protoporphyrin IX which are found in blood, urine, feces of either normal or porphyric subjects are their auto-oxidized products and can not be true intermediates for heme biosynthesis except for Protoporphyrin. Delta aminolevulinic acid (ALA), Porphobilinogen (PBG) and Hydroxymethylbilane have been described as the precursors to porphyrin biosynthesis. Besides the recent advance of porphyrin research within the limit of medical fields the pure organic chemistry of porphyrins symbolized by its large electron conjugated system have been unexpectedly developed for the last 20 years, suggesting that its application will quickly be extended to the new fields of macromolecular engineering and polymer electronics.