527 Purines 



Finally, the occurrence of the adenine nucleotide moiety 

 in various other coenzymes (coenzyme A, flavine-adenine 

 dinuclcotide, DPN, etc.) should not be forgotten. The 

 functions of these coenzymes are considered elsewhere. 



Adenine polyphosphates, then, are so ubiquitous and so 

 metabolically important that they nearly all have been 

 encountered prior to this point in our discussions of mi- 

 crobial metabolism. 



Guanosine polyphosphates, too, are widespread, and 

 they seem to be able to duplicate some of the less specific 

 functions of those of adenine. One reaction in which a 

 guanine polyphosphate is known to participate is : ' 



a-Ketoglutaric Acid + DPN© + CoA-SH -^ 



Succinyl-S-CoA + DPNH + H© + CO2 

 Succinyl-S-CoA + Guanosine Diphosphate + H3PO4 ;=^ 



Succinic Acid + CoA-SH + GTP 



The enzyme catalyzing this reaction has been isolated 

 only from tissues of higher animals, and there is evidence 

 that in Escherichia colt at least the adenine nucleotide 

 seems to be involved.'' 



Guanosine and inosine nucleotides also participate in 

 the formation of phosphoenolpyruvate from oxaloace- 

 tate : " 



Oxaloacetic Acid + GTP :;=± Phosphoenolpyruvic Acid + GDP + COn 



but again this has been shown only in animal tissues. 



The general function of GTP as an energy source in 

 the amination of inosinic acid during adenine biosynthe- 

 sis will be seen later. 



Guanosine diphosphate mannose has been isolated 



" D. R. Sanadl, David M. Gibson, Padmaslni Ayengar and Miriam 

 Jacob, ;. Biol. Chem. 218 505 (1956). 



^ Roberts A. Smith, Irma F. Frank and I. C. Gunsalus, Federation 

 Proc. 16 251 (1957). 



»M. F. Utter and K. Kurahashi, /. Biol. Chem. 207 821 (1954). 



