Pfizer Handbook of Microbial Metabolites 554 



In an Escherichia coli mutant requiring either methi- 

 onine or vitamin B12 for growth methionine synthesis 

 from homocysteine and serine was stimulated by addition 

 of vitamin 612-""' '^ This suggests that again vitamin Bjo 

 may be involved in methyl group synthesis. 



There is some evidence (from higher animals) that 

 there is a folic acid requirement for the introduction into 

 aminoethanol of some, if not all, of the methyl groups of 

 chohne.-" '-^^ 



Little is known about the biosynthesis of pteridines in 

 microorganisms. There are suggestions that both pteri- 

 dines and flavines are related to the purines in this respect. 



•rr^ 



7 4I 5 CH 



Pteridine 



>N T ^6 



Labeled molecule studies with butterflies indicate that 

 carbon atoms 4 and 5 of the pteridine ring in leucopterin 

 and xanthopterin are derived from glycine (4 from the 

 glycine carboxyl group and 5 from the a-carbon atom).-^ 



OH ■■ ^ O" 



O I OH 



N j ] 



N 



H2N H O H2N 



Leucopterin Xanthopterin 



The C-6 position seems to be furnished from carbon diox- 

 ide and the C-2 position from formate, reminiscent of the 

 purines. Carbon atoms 8 and 9 of the pteridine nucleus 



20 c. W. Helliner and D. D. Woods, Biochem. J. 63 26 p (1956). 

 -1 R. L. Kisliuk and D. D. Woods, J. Gen. Microbiol. 18 xv (1957). 

 ^- Jacob A. Stekol, Sidney Weiss and Ethyl I. Anderson, /. Am. 

 Chem. Soc. 77 5192 (1955). 



23 R. Venkataraman and D. M. Greenberg, ibid. 80 2025 (1958). 

 2* F. Weygand and M. Waldschmidt, Angew. Chem. 67 328 (1955). 



