ISSN:
1432-072X
Schlagwort(e):
5-Hydroxybenzimidazolylcobamide
;
Vitamin B12-factor III
;
Coenzyme F420
;
Methanosarcina barkeri
;
Archaebacterium
;
Corrin precursor
;
C-5 pathway
;
Glycine
;
Glutamate
;
Eubacteria
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Abstract Exogenous 5-hydroxy-[2-14C]benzimidazole was transformed by Methanosarcina barkeri into 5-hydroxy-[2-14C]benzimidazolylcobamide. Thereby the endogenous biosynthesis of 5-hydroxybenzimidazole was completely blocked. Benzimidazole and 5,6-dimethylbenzimidazole were used by M. barkeri to form benzimidazolylcobamide respectively 5,6-dimethylbenzimidazolylcobamide (vitamin B12), but in these cases the endogenous biosynthesis of factor III was not completely suppressed. With [2-14C]benzimidazole it was demonstrated that this base as well as the benzimidazolylcobamide formed thereof are no precursors in the biosynthesis of 5-hydroxybenzimidazolylcobamide. Glycine instead was found to be a building block for the biosynthesis of 5-hydroxybenzimidazole, since radioactivity from [1-14C] and [2-14C]glycine was incorporated, into the base moiety of factor III, but not into its corrin moiety. With [1-13C]glycine and 13C-NMR-spectroscopy it was shown that C-1 of glycine gets C-3a of 5-hydroxybenzimidazole. [1-13C]glycine also led to a single prominent signal in the 13C-NMR-spectrum of coenzyme F420, this was assigned to C-10a. Thus C-1 of glycine was incorporated into the hydroxybenzene part of 5-hydroxybenzimidazole, whereas it was not incorporated into this part of coenzyme F420, indicating that the hydroxybenzene part of these two compounds is not formed from a common intermediate. L-[U-14C]glutamate led to the exclusive labeling of the corrin ring of factor III, showing that the corrin precursor 5-aminolevulinic acid is formed by the C-5 pathway in M. barkeri. These experiments indicate that the biosynthesis of factor III in the “archaebacterium” M. barkeri is similar to the corrinoid biosynthesis in the anaerobic “eubacteria” Eubacterium limosum, Clostridium barkeri, and Clostridium thermoaceticum.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00410903
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