FUNCTION 



Nucleotidase 



It is generally assumed that nicotinic acid and nicotinamide are 

 equally effective in the treatment of pellagra and related conditions, 

 and it seems likely that the normal body can convert the acid into the 

 amide and so into the coenzyme. P. J. G. Mann and J. H. Quastel,^^ 

 however, observed one difference between them. Brain extracts 

 contain an enzyme, nucleotidase, which, by hydrolysing cozymase, in- 

 hibited the oxygen uptake of lactic acid in presence of lactic dehydro- 

 genase and cozymase ; nicotinamide, but not nicotinic acid, inhibited 

 the action of nucleotidase on cozyraase. The exact significance of 

 this phenomenon in therapeutics is not clear, but if nicotinamide 

 can prevent the destruction of cozymase, it might explain why cer- 

 tain other substances, such as quinolinic acid, coramine and pyrazine- 

 monocarboxylic acid (see page 288) are effective in pellagra. Other- 

 wise it is difficult to find a satisfactory explanation, since many of 

 these compounds cannot possibly be converted into nicotinamide, 

 although they may well be converted into substances that inhibit 

 nucleotidase. 



Nucleotidase occurs in a large number of animal tissues, lung 

 tissue being especially rich.^^ In the intact cell, the enzyme is 

 kept out of contact with pyridine nucleotides. It is suggested that 

 the release of nucleotidase on damage of the lung may play an im- 

 portant role in the action of some lung irritants. 



An enzyme that liberated nicotinamide from both cozymase and 

 coenzyme II was shown to be present in preparations from the mam- 

 malian central nervous system. ^^ Competition took place between the 

 two coenzymes, so that presumably a common enzyme is concerned ; 

 this may be nucleotidase. 



References to Section 14 



1. O. Warburg and W. Christian, Biochem. Z., 1935, 275, 464. 



2. H. Albus, F. Schlenk and H. von Euler, Z. physiol. Chem., 1935, 



237, I ; Biochem. Z., 1936, 286, 140. 



3. S. Williamson and D. E. Green, /. Biol. Chem., 1940, 135, 345. 



4. F. Schlenk, ibid., 1942, 146, 619 ; F. Schlenk and T. Schlenk, 



Arch. Biochem., 1947, 14, 131. 



5. G. A. Le Page, /. Biol. Chem., 1947, 168, 623. 



6. H. von Euler, P. Karrer and B. Becker, Helv. Chim. Acta, 1936, 



19, 1060. 



7. H. von Euler, F. Schlenk and R. Vestin, Naturwiss., 1937, 25, 318. 



8. F. Schlenk, Arch. Biochem., 1943, 3, 93. 



9. F. Schlenk, Naturwiss., 1937, 26, 668. 



10. R. Vertin, ibid., 667 ; H. von Euler and E. Bauer, Ber., 1938, 71, 

 411 ; H. von Euler and E. Adler, Z. physiol. Chem., 1938, 252, 41. 



279 



