No abstract

Extensive chemical degradation of cobyrinic acid biosynthesized from a sample of factor m radiochemically labeled in its three methyl groups demonstrates that label is retained exclusively in the two methyl groups at positions C-2 and C-7 and confirms that the C-20 methyl group of the precursor is lost during formation of the corrin ring system.

Der „umgedrehte Ring”︁ in Uroporphyrinogen III (Uro'gen III), der Stammverbindung aller natürlichen Porphyrine etc., könnte auf zwei Wegen zustandekommen: 1. durch Isomerisierung eines Kopf‐Schwanz‐verknüpften Bilans wie (1) beim Ringschluß oder 2. durch Bildung einer Vorstufe mit „umgedrehtem”︁ Ring. Nach neuen enzymatischen Studien wird der erste Weg beschritten. magnified image

The “reversed ring” in uroporphyrinogen(III) (uro'gen III), the parent compound of all natural porphyrins, etc., could arise in two different ways: (i) by isomerization of a head‐to‐tail linked bilane such as (1) on ring closure or (ii) by formation of a precursor with a “reversed” ring. Enzymatic studies now show the former route to apply.