Pfizer Handbook of Microbial Metabolites 514 



ated to the triphosphate by ATP, making the process a 

 catalytic one. 



The function of the CDP-ribitol and CDP-glycerol in 

 Lactobacillus arabinosus seems to be to donate these two 

 reduced sugar phosphates in the formation of polymers. 

 These ribitol-glycerol-phosphate polymers are components 

 of the cell walls of bacteria. Several references are given 

 in Appendix A to structural studies on these substances. 



Biosynthesis of the pyrimidines seems to take a similar 

 course in microorganisms and in higher animals. So 

 many workers have contributed to our knowledge of this 

 scheme that referencing cannot be included, but in out- 

 line what is now believed to be the important pathway is 

 shown below: 



Carbamyl Phosphate 

 O 



II 

 H2N— C— OPO3H2 H3PO4 



HOOC— CH2— CH— COOH -^^ ^- — ► 



I aspartic transcarbamylase 



NHo 



L-Aspartic Acid 



O 



II 

 HO— C 



\ H2O 



H2N CH2 ^ » 



I I dihydro- 



C CH orotase 



O JJ COOH 



N-Carbamyl-l 



aspartic Acid 



(Ureidosuccinic Acid) 



O 



'^\ DPN® DPNH + H® 



HN CHo 



C CH dihydroorotic 



^ \.Ki/^ \ dehydrogenase 



O 'J COOH 



n 



L-Dihydroorotic 

 Acid 



