BIOSYNTHESIS OF PENTOSES 275 



from pigeon liver.^^^ In the presence of adenine and "nucleotide phosphory- 

 lase," ribose diphosphate is converted into adenosine monophosphate/** 

 thus supporting Greenberg's suggestions*^ that purines can be incorporated 

 directly into nucleotides without prior formation of nucleosides. The 

 coenzyme function of ribose diphosphate in phosphoribomutase and phos- 

 phoglucomutase reactions has been reported in some detail. ^^^ 



i« E. Scarano, Nature 172, 951 (1953). 



"« M. Saffran and E. Scarano, Nature 172, 949 (1953). 



^" G. R. Greenberg, J. Biol. Chem. 190, 611 (1951). 



1** H. Klenow, Arch. Biochem. and Biophys. 46, 186 (1953). 



