BIOSYNTHESIS OF NUCLEOSIDES AND NUCLEOTIDES 339 



Phosphate Transfer Enzymes 



The phosphate transfer enzymes, first reported in germinating barley, 

 have now been found also in human prostate and in rat fiver. '^* The barley 

 and liver enzymes produce only the 5-nucleotides whereas the prostate 

 enzyme converts the nucleosides into all possible mononucleotide isomers. 

 Besides phenyl phosphate, 5-nucleotides can serve as phosphate donors with 

 the barley and liver enzyme. 



Phosphorihokinase and Nucleotide Phosphorylase 



Kalckar and his co-workers have presented new information on 5-adenylic 

 acid formation. ^^^-'^^ Pigeon liver enzyme contains 5-phosphoribokinase 

 which catalyzes the following reaction: 



Ribose-5-phosphate + ATP ^ ribose-l,5-diphosphate -|- ADP (27) 



Another enzyme from the same source, termed nucleotide phosphorylase* 

 brings about the reaction: 



Ribose-l,5-diphosphate + adenine ;=^ 5-adenylic acid -f phosphate (28) 



>" G. Brawerman and E. Chargaff, /. Am. Chem. Soc. 75, 4113 (1953). 

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



