Structure of the adenylcobamide coenzyme: degradation by cyanide, acid, and light.

The isolation of an adenylcobamide coenzyme that is required for the interconversion of glutamate and ,8-methylaspartate by a bacterial enzyme system has been described and some properties of the coenzyme have been reported (1, 2). The spectrum of the coenzyme is very different from that of the cobamide vitamins, such as cyanocobalamin (5,6-dimethylbenzimidazolylcobamide cyanide, vitamin Big) and pseudovitamin Blz (adenylcobamide cyanide). The latter compounds and their previously known derivatives have a prominent absorbancy maximum in the 350to 367-rnp region of the spectrum, which is entirely lacking in the adenylcobamide coenzyme. The coenzyme differs chemically from pseudovitamin Blz by containing not one but two adenine moieties. Exposure of the coenzyme to cyanide, acid, or visible light causes inactivation and modification of the spectrum to a shape characteristic of the appropriate form of cobamide vitamin. This change in spectrum has been found also to be associated with a release of adenine or an adenine derivative. The present paper describes some of the chemical changes that accompany inactivation of the coenzyme by cyanide, acid, and light, and interprets these results in terms of the coenzyme structure.