55 Aliphatic Acids and Glycolipides 



palmitic acid was incorporated into mycolic acid, and the prod- 

 uct degraded to show that the carboxyl group and the oxidized 

 C-atom Ij-to it in the corynomycolic acid were labeled. A similar 

 biosynthetic path was suggested for the higher molecular weight 

 mycolic acids produced by mycobacteria. Thus, condensation 

 of 2 moles of n-C-c and 2 moles of n-C,s acids would yield the 

 Css mycolic acids of cord factor. A C^f, acid is known to be pro- 

 duced by mycobacteria, and a C-.o acid, corynine, by corynebac- 

 teria. 



The biotin requirement for enzymatic carboxylations is be- 

 coming generally recognized. It was in connection with his 

 studies in lipide metabolism that Lynen isolated and synthesized 

 a reaction product of biotin and carbon dioxide in which COo 

 had reacted at one of the nitrogen atoms to give an allophanic 

 acid type of intermediate, the side-chain carboxyl group perhaps 



11 Hooc ;i 



/^\ \ /^\ 



HN N— COOH N NH 



II II 

 CH CH or CH CH 



CH2 CH— (CH,),— COOH CH2 CH— (CH2)4— COOH 



being bound to the protein apoenzyme by an amide bond. 



An intermediate may be adenosine diphosphoryl biotin (from 

 ATP): 



O OH OH O 



II I I II ^ 



/C\ /P—O—P—O— Adenosine ^Cv /COO© 



HN N ^ ^ HN' N +Adenosine- 



I I + CO2 — > I I diphosphate 



CH CH CH CH 



Other suggestions concerning the detailed function of this 

 carboxylase cofactor were made.-' 



The lecithins are formed by initial ATP phosphorylation of 

 one glycerol hydroxyl group followed by esterification of the re- 



-^ F. Lynen, J. Knappe, E. Lorch, G. Jutting and E. Ringelmann, 

 Angew. Chem. 71 481 (1959). 



