Pfizer Handbook of Microbial Metabolites 314 



diates have been suggested as precursors of 2,6-dipicolinic acid, 

 which is formed in some bacterial spores. Free diaminopimelic 



O 



II 



c 



CHo CHo 



HOOC— I I — > /^N- 



CH C HOOC COOH 



\ ■i^\ Dipicolinic Acid 



NH2 O COOH 



acid has been isolated from vegetative cells of such spore-form- 

 ers. It has never been found in yeasts and molds. 



a,£-Diaminopimelic acid replaces lysine in the repeating pen- 

 tapeptide unit of the bacterial cell wall in Corynehacterium 

 diphtheriae , E. coli and certain other bacteria (especially gram 

 negatives). Some E. coli strains accumulate considerable quan- 

 tities of diaminopimelic acid, and this faculty has been ex- 

 ploited in a two-step commercial production process. 



Many microorganisms metabolize lysine to pipecolic acid, a 

 component of several antibiotics. 



CH2 



CH2 CH2 



-"' o. 



CHo CH— COOH ^N' 



\ / H COOH 



_ NH2 NH2 Pipecolic Acid 

 Lysine 



The amino acids discussed to date are closely integrated with 

 carbohydrate and fat metabolism. Those remaining to be con- 

 sidered are more remotely derived. 



Valine, isoleucine and leucine are essential to the mammalian 

 diet and are required also by many microorganisms. This 

 seems to indicate enzymatic difficulties in the biosynthesis of 

 these branched-chain amino acids. 



Much evidence has accumulated concerning the biosynthesis 

 of valine and isoleucine, and the following pathway is indi- 

 cated (for valine): 



