BlOdKXESIS OF ANTIBIOTICS 



69 



and glutamic acid) permitted the highest 

 level (1000 to 3000 fig per ml) of strepto- 

 mycin synthesis by the 8+ culture. Xor- 

 leucine and isoleucine strongly inhibited 

 streptomycin synthesis in experiments with 

 growing cells as well as with resting cells; 

 leucine stimulated synthesis. Resting cell 

 data also suggested that acetate is an inter- 

 mediate in streptomycin biosynthesis. 



Silverman and Rieder (19(30) utilized the 

 distribution of radioactivity among the 

 individual carbon atoms to elucidate the 

 mechanism of the formation of X-methyl-L- 

 glucosamine in the streptomycin molecule 

 from D-glucose. Both D-glucose-l-C'' and 

 D-glucose-6-C^^ were employed. A method 

 for the isolation of the methyl glucosamine 

 was described, as was a procedure for the 

 degradation of this amino sugar. The conclu- 

 sion was reached that the major portion of 

 the radioactivity incorporated into the 

 carbon chain of the amino sugar was in 

 carbon 1 when D-glucose- l-C'"* was used and 

 in carbon 6 when D-glucose-6-C^'* was em- 

 ployed. 



These investigators suggested that a pos- 

 sible mechanism for the inversion of all the 



asymmetric carbons of D-glucosc is one of 

 multiple epimerizations. Other possibilities 

 were also suggested, such as an extensive 

 series of oxidations and reductions with 

 subseciuent inversion of configuration upon 

 reduction, or a mechanism of multiple isom- 

 erizations. 



The changes occurring during strepto- 

 mycin production are shown in Table 21. 

 Little progress has so far been made in the 

 use of precursors for streptomycin biosyn- 

 thesis. By using C'^^ compounds, it was shown 

 (Hunter et al., 1904) that the guanidine 

 carbon is derived largely, if not entirely, 

 from CO2 , and that compounds such as 

 arginine may act as precursors. The strep- 

 tamine and streptose portions of the strep- 

 tomycin mf)lecule appear to be formed from 

 glucose (Hunter and Hockenhull, 1955). 

 Streptamine itself does not act as a pre- 

 cursor, but X-methyl-L-glucosamine does. 

 According to Egorov (1957), a combination 

 of a guanidine compound (L-arginine, 

 creatine, guanidine) and inositol favors the 

 biosynthesis of streptomycin. Asparagine 

 favors growth l)Ut not streptomycin synthe- 

 sis. Hydrolysates oi casein and soybean 



Table 21 



Changes occurring during feriucntation of glucose -meal exlracl-peplone medium 

 (Dulaney and Perlman, 1947) 

 Medium: Glucose 1 per cent, meat extract 0.5 per cent, peptone 0.5 per cent, sodium chloride 0.5 

 per cent. 



Mj'celium (mg/ml) 



Streptomycin (mg/liter) . , 



Glucose (mg/ml) 



Soluble C (mg/ml) 



Lactic acid (mg/liter) . . . . 

 Oxygen demand (Qoo/ml) 



Soluble N (mg/ml) 



Mycelial N (mg/ml) 



Inorganic P (mg/ml) 



Ammonia N (mg/liter) . . . 

 pH 



Duration of fermentation (days) 



9.0 

 10.2 

 292 



1.48 



118 



66 



7.35 



0.4 





 8.8 

 8.6 

 328 



19 

 1.30 

 0.04 

 108 



70 

 7.30 



5.1 



37 

 8.0 

 7.0 

 114 



81 

 1.10 

 0.44 



34 



75 

 7.55 



5.8 

 194 



2.4 



5.1 

 13 

 82 



0.67 



0.62 



1 



63 



7.50 



5.7 



198 



1.2 



5.0 



10 



53 



0.70 



0.57 



5 



103 



7.75 



4.8 

 231 

 0.6 

 4.4 

 16 

 25 

 0.73 

 0.49 

 2 

 115 

 8.25 



4.6 

 270 



4.6 



12 



5 



0.90 



0.40 



19 



179 



8.55 



4.2 



186 



4.5 



6 



0.88 



0.38 



24 



232 



8.65 



3.8 

 267 



4.6 

 15 



1.14 

 0.29 

 34 

 265 

 8.90 



