METABOLISM OF THE NUCLEIC ACIDS 417 



stituent of PXA by lyophilized preparations of Staphylococcus aureus. 

 About the same time, Gros and Macheboeuf'^^'-* found that penicillin 

 exhibited an inhibitory effect on the catabolism of adenylic, guanylic, and 

 uridylic acids by Clostridium sporogenes. Soon after these findings, Mitchell 

 et a/.'-^'" observed that, immediately after the addition of penicillin to 

 growing cultures of S. aureus, a progressive disturbance occurred in the 

 relationship between extractable nucleotides and the nucleic acids of the 

 organisms, due apparently to a very considerable increase in the amount 

 of nucleotides extractable from the cells. This accumulation appeared to be 

 the result of a decreased rate of incorporation into the nucleic acid mole- 

 cules rather than to an increase in the rate of synthesis of nucleotides. 

 Park and Johnson, '^^ in studies on the nucleotide fraction of S. aureus grow- 

 ing in the presence and absence of penicillin, noticed an accumulation of 

 labile organic phosphate with an absorption maximum at 262 m/x. Sub- 

 sequent work by Park^^^"'^^ resulted in the isolation of three uridine pyro- 

 phosphate derivatives from acid extracts of the penicillin-treated cells. 

 The first of these compounds was shown to be uridine pyrophosphate 

 attached to an A^-acetylamino sugar, while the second contained the uridine 

 pyrophosphate A^'-acetylamino sugar combined with L-alanine. The third 

 derivative, which may not be a single substance, appeared to consist of a 

 peptide attached to the uridine pyrophosphate A^-acetylamino sugar as 

 before. This peptide is composed of one L-lysine, one D-glutamic acid, and 

 three alanine residues. Park^^^ suggests that these compounds may occur 

 naturally in normal S. aureus cells but that they accumulate in penicillin- 

 treated cells because of an inability to metabolize them further. In an 

 attempt to isolate these substances from normal cells. Park obtained a 

 very srnall amount of three substances which corresponded to the three 

 isolated from the penicillin-treated cells, but there was insufficient material 

 to prove that the two groups of material were identical. However, if, as 

 seems likely, these three substances are present even in minute amounts 

 in normal bacterial cells, it is reasonable to suppose that penicillin in some 

 way affects the system which normally metabolizes them. From the quan- 



" F. Gros and M. Macheboeuf, Ann. inst. Pasteur. 74, 308 (1948). 



" F. Gros and M. Macheboeuf, Bull. acad. med. (Paris) 5, 80 (1948). 



" F. Gros and M. Macheboeuf, Compt. rend. 224, 858 (1949). 



2« P. Mitchell, Nature 164, 259 (1949). 



" P. Mitchell and J. Movie, J. Gen. Microbiol. 5, 421 (1951). 



28 J. T. Park and M. J. Johnson. J. Biol. Chem. 179, 585 (1949). 



J. T. Park, in "Phosphorus Metabolism" (McElroy and Glass, eds.), Vol. 1, p. 93. 



Johns Hopkins Press, Baltimore, 1951. 

 »» J. T. Park, J. Biol. Chem. 194, 877 (1952). 

 «i J. T. Park, J. Biol. Chem. 194, 885 (1952). 

 32 J. T. Park, J. Biol. Chem. 194, 897 (1952). 

 " J. T. Park, 2nd Intern. Congr. Biochem., Paris p. 31 (1952). 



