Purification and properties of cobamide coenzymes obtained from Propionibacterium arabinosum.

Propionibacterium arabinosum is known to produce an adeninylcobamide when grown in a medium containing yeast extract or corn steep-liquor (I, 2). Such a medium, although not intentionally fortified with a heterocyclic base, undoubtedly contains substantial amounts of adenine or its derivatives. Addition of an appropriate benzimidazole, purine, or other heterocyclic base to the medium, or to a suspension of washed bacteria (1, 2), results in more or less complete replacement of the adenine moiety of the cobamide by the added base. Consequently, if P. arobinosum, like Clostridium tetanomorphum, is able to synthesize the adeninylcobamide coenzyme, it should also be able under suitable conditions to synthesize a variety of other cobamide coenzyme analogues. Such a “directed synthesis” of 5,6-dimethylbenzimidazolylcobamide and benzimidazolylcobamide coenzymes by C. tetanomorphum has previously been reported (3, 4). This paper describes the purification and some properties of several additional cobamide coenzymes obtained from cells of P. arabinosum exposed to various heterocyclic bases.