594 G. SCHMIDT 



activity is of interest as a mechanism for the biosynthesis of nucleotides. 

 The donor requirements are different for different phosphatases. 5'-Nucleo- 

 tides are particularly efficient donors with malt phosphatase as the transfer 

 enzyme, but ineffective with prostate phosphatase. ^^''^ On the other hand, 

 phenyl phosphate is a good phosphoryl donor with prostate phosphatase. 

 No essential differences between the efficiency of various donors were found 

 for liver phosphatase. ^^^= 



The structure of the nucleotides formed was different according to the 

 nature of the transferring phosphatases. With the barley phosphatase, only 

 5'-nucleotides were obtained (e.g., 5'-cytidylic, 5'-thymidylic acids), 

 whereas with prostate phosphatase, all three isomers of each nucleotide 

 were obtained. Between 5 and 10% of the added nucleosides (in 40 milf 

 concentrations) were phosphorylated at donor concentrations of approxi- 

 mately 200 mM. 



IV. Nucleoside Kinases 



Adenosine kinase was discovered in yeast by Ostern, Baranowski, and 

 Terszakowec,^^^*^ in 1938 and partially purified by Caputto^^'** and by Rom- 

 berg and Pricer^^^f in 1951, who demonstrated also the presence of a different 

 kinase in some animal tissues. It catalyzes the reaction: 



adenosine -|- ATP = AMP + ADP 



pH Optima. The pH optimum of the yeast enzyme is between 6.9 and 7 ; 

 that of the liver enzyme lies between 4.9 and 5.0. 



Specificity. The yeast enzyme, as well as the liver enzyme, is specific for 

 adenosine and for 2 , 6-diaminopurine riboside. ^^*^ No phosphorylation of 

 guanosine, inosine, uridine, or cytidine could be detected. 



Activators. The yeast enzyme is optimally activated by 0.02 M magne- 

 sium ions or by 0.002 M manganese ions. The enzyme can be stabilized by 

 reduced glutathione or by an unknown stabilizing factor present in boiled 

 yeast extracts. 



Assay. According to Ostern et al.^^*'^ acetone-dried yeast is sufficiently 

 active to permit the isolation of 5'-adenylic acid in good yield in large-scale 

 experiments with adenosine as substrate. 



In maceration juice or extracts of animal tissues, the enzyme can only be 

 detected after a preceding purification designed to remove contaminating 

 enzymes. Caputto used in his assay procedures manometric determinations 

 of 5'-adenylic deaminase, phosphate balances, or chromatography, and he 

 succeeded in the quantitative analytical separation of adenosine and the 



'"d P. Ostern, T. Baranowski, and J. Terszakowec, Z. physiol. Chem. 251, 258 (1938). 



i"«R. Caputto, J. Biol. Chem. 189, 801 (1951). 



'"f A. Kornberg and W. E. Pricer, /. Biol. Chem. 193, 481 (1951). 



