39. ANTIMETABOLITES AND NUCLEIC ACID METABOLISM 493 



fresh medium. 258, 260 Such a circumstance is similar to that seen with chlor- 

 amphenicol, in which abnormal RNA is formed and protein synthesis is 

 interrupted. Azaguanine also blocks the adaptive formation of amylase in 

 B. subtilis, 28 * as well as that of 0-galactosidase and catalase in a strain of 

 S. aureus. 2 * 7 • 288 The production of antibodies by mice 289 in vivo and by rab- 

 bit spleen in vitro 290 also has been shown to be blocked by azaguanine; 

 however, these observations must be examined at the enzyme level before 

 the analog or its derivatives can be assigned a direct causal relationship to 

 the phenomena. 



4. DlAMINOPURINE 



Consideration of 2,6-diaminopurine (XII) as an agent which can inter- 

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 a precursor of purines, particularly guanine, in most mammalian 291 - 297 and 

 some bacterial systems. 298 ' 301 Nevertheless, this amino derivative of guanine 

 is a good inhibitor of the growth of certain bacteria, 302-304 viruses, 305, 306 and 

 animal tissues, 307 " 312 possibly through an interference with some aspect of 



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