IV. BIOCHEMICAL SYSTEMS 485 



The structural formula listed above is now firmly established for the 

 oxidized form of DPN. This formula was established in the following way. 



1. Acid hydrolysis splits the molecule to yield nicotinamide,^' ^ adenine,^" 

 and 2 molecules of ribose-5-phosphate.^^ • ^- 



2. Hydrolysis by weak alkali at low temperature splits off nicotinamide 

 and leaves adenosinediphosphate ribose moiety .^^ 



3. Hydrolysis with weak alkali at high temperature yields adenosine- 

 diphosphate.-^ 



4. Enzymatic hydrolysis under certain conditions yields nicotinamide 

 riboside and adenosine.-^ 



5. The fact that phosphate was linked to ribose in the 5 position was 

 shown by von Euler ei al.,-^ since the pentose phosphate from DPN gave 

 no formaldehyde when reacted with periodic acid. 



6. D-Ribose was already known to be the carbohydrate of adenosine. ^^ 

 Von Euler et al.-^ partially hydrolyzed DPN with acid, treated with 



phosphatase, and isolated a pentose, the phenylosazone of which was iden- 

 tical with D-ribose. As pointed out by Schlenk,^- these workers did not 

 establish that the ribose came from the nicotinamide-linked portion of the 

 molecule and furthermore the phenylosazones of D-ribose and D-arabinose 

 are identical. He, however, reached the same conclusion by isolating the 

 pentose from nicotinamide nucleoside (step 4) and forming the p-bromo- 

 phenylhydrazone and studying its other properties. In addition, he con- 

 firmed the linkage of ribose and phosphate in the 5 position of ribose. 



Thus the structural formula for DPN as proposed originally in 1936-^"^^ 

 seems well established. It should be noted, however, that the customary 



>6 S. Ochoa and C. G. Ochoa, Nature 140, 1097 (1937). 



" O. Meyerhof and P. Ohlmeyer, Biochem. Z. 290, 334 (1937). 



'8 H. von Euler, A?i(iew. Chem. 50, 831 (1937). 



'^ H. von Euler, F. Schlenk, H. Heiwinkel, and B. Hogberg, Hoppe-Seyler's Z. 



physiol. Chem. 256, 208 (19.38). 

 20 H. von Euler and K. Myrback, Hoppe-Seyler's Z. physiol. Chem. 177, 237 (1928); 



Naturwissenschaften n, 291 (1929). 

 2' F. Schlenk, Arkiv Kemi, Mineral. Geol. 12B, 20 (1936). 



22 F. Schlenk, J. Biol. Chem. 146, 619 (1942). 



23 F. Schlenk, H. von Euler, H. Heiwinkel, W. Gleim, and H. Nystrom, Hoppe-Sey- 

 ler's Z. phrjsiol. Chem. 247, 23 (1937). 



24 R. Vestin, F. Schlenk, and H. von Euler, Ber. 70, 1369 (1937). 



25 F. Schlenk, Naturwissenschaften 28, 46 (1940); Arch. Biochem. 3, 93 (1943). 



26 H. von Euler, P. Karrer and B. Becker, Helv. Chim. Acta 19, 1060 (1936). 



2^ P. A. Levene and L. W. Bass, Nucleic Acids. American Chemical Society Mono- 

 graph xNo. 56, New York, 1931. 



28 II. von Euler, H. Karrer, and E. Usteri, Helv. Chim. Acta 25, 323 (1942). 



29 F. Schlenk and H. von Euler, Naturwissenschaften 24, 794 (1936). 



'" II. von Euler and F. Schlenk, Hoppe-Seyler's Z. physiol. Chem. 246, 64 (1937). 



3' K. Myrback, Tabulae Biol. 14, 110 (1937). 



32 L. J. Haynes and A. R. Todd, J. Chem. Soc. 1950, 303. 



