Pfizer Handbook of Microbial Metabolites 



420 



teine,'' methionine,* glutathione* and acetate. Some of 

 these rejected intermediates are shown: 



HO 



Lanthionine and /?-methyllanthionine occur in several 

 other polypeptide antibiotics (subtilin, duramycin, cinna- 

 mycin, nisins). Certain of these compounds are incor- 

 porated to some extent, but only indirectly. 



Some evidence is being accumulated concerning the 

 actual peptide intermediate. The dipeptide L-cystinyl- 

 L-(COOH — C^*) valine is a better penicillin precursor than 

 L-(COOH — C'*) valine alone, while the reverse is true for 

 protein synthesis.*' (L-Cystine can be reduced to L-cys- 

 teine by the mold.) 



HOOC— CH— CH2— S 



I 

 NHo 



S— CH2— CH— CO— NH— CH— COOH 



I 1 



NH2 CH 



CHs CHs 



L-CystinyI-L-(COOH— C'^) valine 

 ^ Carl M. Stevens, Pran Vohra, Joseph E. Moore and Chester W. 

 DeLong, ibid. 210 713 (1954). 



6 H. R. V. Arnsteln and D. Morris, Biochem. ]. 71 8p (1959). 



