328 F. SCHLENK 



tidase was accumulated by Reis,^" GuUand and Jackson,®^ and Mann.*^ ^ 

 fiftyfold purification and separation from other phosphatases has recently 

 been accomphshed by Heppel and Hilmoe,*^ who used bull seminal plasma 

 as a source material. The enzyme has a pH optimum at 8.2 and shows 

 specificity toward the following ribose-5-phosphate derivatives, with de- 

 creasing activity in the order given: cytidine-5'-phosphate, uridine-5'-phos- 

 phate, inosine-5'-phosphate, adenosine-5'-phosphate, and, to a lesser degree, 

 ribose-5-phosphate. No splitting with numerous other phosphate esters 

 including adenosine-2'- and 3'-phosphate, guanylic, uridylic, and cytidylic 

 acids from yeast was observed. The enzyme was also found in snake venoms 

 and in potato extracts.^^'*''^^^'*' 



The significance of 5-nucleotidase in nucleotide metaboUsm is suggested 

 by its specificity. About its role in synthetic processes as little can be stated 

 as about other hydrolytic enzymes. Moreover, we do not know whether 

 5-nucleotides or 3-nucleotides are the primary products employed by nature 

 in polynucleotide synthesis. 



Shuster andKaplan^"* have found a 3-nucleotidase in germinating barley. 

 They separated it from 5-nucleotidase and nonspecific phosphatases and 

 observed that 3-adenyUc, 3-guanylic, and 3-inosinic acids are split rapidly. 

 3-Uridylic acid and 3-cytidylic acid are split more slowly. 



b. Adenosine Phosphokinase 



Ostern and co-workers^* have suggested an interconversion of adenosine 

 3'-phosphate and adenosine-5'-phosphate with adenosine as an interme- 

 diate. They were concerned mainly with the origin of coenzyme adenylic 

 acid, which they assumed to arise from ribonucleic acid via adenosine. 

 Adenosine phosphates were found to accumulate, if adenosine was incor- 

 porated into fermenting yeast macerates; ribonuclease and phosphatase 

 action were assumed to provide the adenosine in cells from polynucleotides. 

 However, it is not certain that ribonucleic acid supplies coenzyme moieties; 

 the reverse could be assumed as well. Ostern 's experiments were carried out 

 before tracer techniques were available. Recent results make it probable 

 that coenzyme and polynucleotide synthesis are not intimately related. 



8» J. Reis, Bull. soc. chim. hiol. 16, 7, 385 (1934); 22, 36 (1940); Enzymologia 2, 183 



(1937); 5, 25 (1938). 

 " J. M. Gulland and E. M. Jackson, Biochem. J. 32, 597 (1938). 

 82 T. Mann, Biochem. J. 39, 451 (1945). 



8' L. A. Heppel and R. J. Hilmoe, /. Biol. Chem. 188, 665 (1951). 

 83" F. G. Fischer and H. Dorfel, Z. physiol. Chem. 296, 232 (1954). 

 8'b M. Hartmann and W. Bosshard, Helv. Chim. Acta 21, 1554 (1938). 

 8^ L. Shuster and N. O. Kaplan, J. Biol. Chem. 201, 535 (1953). 

 86 P. Ostern and J. Terszakowec, Z. physiol. Chem. 250, 155 (1937); P. Ostern, T. 



Baranowski, and J. Terszakowec, ibid. 251, 258 (1938); P. Ostern, J. Terszakowec, 



and S. Hubl, ibid. 255, 104 (1938). 



