Schulze B, Ruoff D, Volger B, Renz P
Institut für Biologische Chemie und Ernährungswissenschaft, Universität Hohenheim, Stuttgart, Germany.
Biol Chem Hoppe Seyler. 1994 Nov;375(11):785-8.
The transformation of [1-15N]5-hydroxybenzimidazole and [1-15N]5-hydroxy-6-methylbenzimidazole into the 5,6-dimethylbenzimidazole moiety of vitamin B12 by Eubacterium limosum-cultures was studied. The vitamin B12 obtained was exclusively 15N-labeled in N-1 of the base part, as revealed by NMR-measurements. This indicates that either the unsubstituted 5,6-dimethylbenzimidazole presumably formed is not released from the enzyme until the ribose-5'-phosphate substituent is introduced, or that the precursors are first transformed into their alpha-nucleotide-5'-phosphates which then react to form 5,6-dimethylbenzimidazole-alpha-D-ribofuranoside- 5'-phosphate (alpha-ribazole-5'-phosphate).
研究了[1-¹⁵N]5-羟基苯并咪唑和[1-¹⁵N]5-羟基-6-甲基苯并咪唑被黏滞真杆菌培养物转化为维生素B12的5,6-二甲基苯并咪唑部分的过程。核磁共振测量结果显示，所获得的维生素B12仅在碱基部分的N-1位被¹⁵N标记。这表明，要么推测形成的未取代5,6-二甲基苯并咪唑在引入核糖-5'-磷酸取代基之前不会从酶中释放出来，要么前体首先转化为它们的α-核苷酸-5'-磷酸，然后反应形成5,6-二甲基苯并咪唑-α-D-呋喃核糖苷-5'-磷酸（α-核唑-5'-磷酸）。
