74 



NATURE, FORMATION, AND ACTIVITIES 



Days 



13 



Figure 2. Effect of arseiiite on the accumula- 

 tion of pyruvate in a submerged culture of S. 

 erythreus. (Reproduced from Musilek, V. and 

 Sevcik, V. Symposium on antil)i(itics, Prague 

 Al)str., p. 32, 1959.) 



of O.o per cent sodium acetate or propionate 

 markedly reduced the inhibitory effect of 

 arsenite on the biosynthesis of erythromycin. 

 Other salts of organic acids, as well as gly- 

 cine, failed to nullify the effect of arsenite. 

 The latter completely inhibited the oxidative 

 decarboxylation of pyruvate and oxidation 

 of acetate by washed suspensions of *S'. 

 erythreus. Oxidation of glucose was only 

 partially inhibited. It was therefore con- 

 cluded that the biosynthesis of erythromycin 

 is dependent on the oxidative decarboxyla- 

 tion of pyruvic acid to acetic acid. The par- 

 ticipation of acetic acid as the initial sub- 

 strate for the biosynthesis of propionic acid, 

 presumed to be the precursor of the lactone 

 nucleus of the erythromycin molecule, was 

 suggested (Musilek and Sevcik, lOoSb). 



According to .Musilek et al. (]9o8), the 

 })iosynthesis of acetylmethylcarbinol de- 

 pends largely on the composition of the 

 medium and on the presence of arsenite, 

 which regulates the metabolism of pyruvic 

 acid. In the case of S. aureofacicns, the 

 stimulating effect of phosphate on the pro- 

 duction of acetylmethylcarbinol suggested a 

 partial explanation of the negative effect of 

 phosphate on the biosynthesis of chlortetra- 

 cycline (see also Biffi et al., 19o4). The addi- 

 tion of arsenite to a submerged culture of 

 S. erythreus reduced erythromycin produc- 

 tion by nearly 90 per cent, but vitamin B]2 

 production and growth were reduced by only 

 20 per cent. No direct relationship could 

 thus be demonstrated between the produc- 

 tion of erythromycin and of B12 (Alusilek, 

 1959). 



The addition to submerged culture of 

 arsenite, which inhibits the second step 

 of oxidative decarboxylation of pjTUvic acid 

 to acetic acid {i.e., the oxidation of acetal- 

 dehyde), allows the accumulation of pyruvic 

 acid and acetaldehyde at the beginning, but 

 the anoxidative process of biosynthesis of 

 acetylmethylcarbinol from these substrates 

 is intensified. The inhibitory effect of arse- 

 nite on erythromycin biosynthesis is sup- 

 pressed to a large degree not only by the 

 addition of sodium acetate and propionate 

 but also by sodium formate. This suggested 

 that formic acid or its metabolically active 

 equivalent {e.g., formaldehyde) is closely 

 connected with the biosynthesis of erythro- 

 mycin. When washed mycelium was used, 

 the anoxidative biosynthesis of acetyl- 

 methylcarbinol from free acetaldehyde took 

 place. Tnlike the oxidation of acetaldehyde, 

 the oxidation of succinate was not inhibited 

 by arsenite. These results pointed further to 

 the essentiality of acetic acid as an inter- 

 mediate of erythromycin biosynthesis (Mu- 

 silek and 8e\'cik, 19")9). 



Chain (19r)8) postulated the mechanism 

 of the biosvnthesis of ervthromvcin as fol- 



