Pfizer Handbook of Microbial Metabolites 



446 



groups as shown below. A labeling experiment has shown 

 that 



HOOC— CH,— CH,— CO— S— CoA 



CH3 



® 



— C— S— CoA 



migration 



HOOC— CH— CO— S— CoA 



@ — COOH 

 ,, migration 



HOOC— CH,— CH2— CO— S— CoA 



is the actual process.^" A free radical mechanism was 

 proposed in which the Co*""^ of the cobamide coenzyme 

 initiates the one-electron transfer: 



S— CoA 



S— CoA 



This is analogous to a rearrangement reported earlier by 

 Urry and Kharasch.-^'^ 



The same organism (Clostridiian tetanomorphiim) was 

 found capable of producing coenzymes containing the 

 benzimidazole and dimethylbenzimidazole forms of vita- 

 min Bjo.'^ The dimethylbenzimidazole coenzyme has been 

 found'^' to promote the equilibrium reaiTangement previ- 

 ously known to exist:''* 



5° H. Eggerer, P. Overath and F. Lynen, /. Am. Chem. Soc. 82 2643 

 (1960). 



SI W. H. Urry and M. S. Kharasch, ibid. 66 1438 (1944). 



^^ H. Weissbach, J. Toohey and H. A. Barker, Proc. Nat. Acad. Sci. 

 45 521 (1959). 



''^ E. R. Stadtman, P. Overath, H. Eggerer and F. Lynen, Biochem. 

 and Biophys. Res. Comms. 2 1 (I960); Joseph R. Stern and Daniel L. 

 Friedman, ibid. 2 82 (I960); Shantov Gurnani, S. P. Mistry and 

 B. Connor Johnston, Biochim. et Biophys. Acta 38 187 (1960). 



•'* Robert W. Swlck and Harland G. Wood, Proc. Nat. Acad. Sci. 

 U. S. 46 28 (1960). 



