IV. BIOCHEMICAL SYSTEMS 



483 



barium salt of DPN is easily soluble in dilute alcohol. According to Le- 

 Page,'- when 3 volumes of alcohol are added to a water solution of DPN 

 and TPN at pH 9 in the cold, DPN is soluble to the extent of 5 mg. per 

 milliliter or greater while TPN is quantitatively precipitated. Ochoa^^ was 

 able to isolate DPN from rabbit muscle in good yield and in "pure" form 

 by modifying the procedure of Meyerhof and Ohlmeyer.'* 



In the light of more recent information, it is doubtful if any of these 

 "pure" preparations of the early workers were actually pure in the chemical 



TABLE VII 

 Concentration of DPN and TPN in Various Materials (adapted from 



F. Schlenk^*'') 

 (7/g. of fresh weight) 



DPN 



TPN 



Brewer's yeast 



Baker's yeast 



Muscle (striated rabbit) 



Liver (rat) 



Kidney (rat) 



Muscle (rat) 



Muscle (human) 



Liver (cat) 



Thigh (cat) 



Oxyntic cells, stomach (cat) 



Retina (cattle) 



Erythrocytes (human) 



Erj^throcytes (horse) 



Erythrocytes (rat) 



Lobster, Homarus vulgaris, tail 



Chilomonas Paramecium 



Pollen {Salix, Populus) 



" Per gram of fat-free and dry tissue. 



sense, although they may have been pure from the biochemical standpoint. 

 A possible exception to this is the work of Ohlmeyer,^^ who isolated DPNH2 

 from a purified DPN preparation. The high molecular extinction coeffi- 



12 G. A. LePage in Respiratory Enzymes, p. 87. Burgess Publishing Co., Minneapolis, 

 1949. 



'^S. Ochoa, Biochcm. Z. 292, 68 (1937). 



'^ O. Meyerhof and P. Ohlmeyer, Pflugers Arch. ges. Physiol. 188, 114 (1921). 



15 P. Ohlmeyer, Biochem. Z. 297, 66 (1938). 



15a j^ Wallenfels and W. Christian [Angew. Cheni. 64, 419 (1952)] have recently 

 announced the crystallization of DPN as a quinine salt. This product crystallized 

 as fine, almost featherlike needles arranged in sheaves and gave a melting point 

 between 162 and 170° with decomposition. Using pure DPN recovered from the 

 crystallized salt, they ol)tained an extinction coefficient of 9.43 cm.^ per milligram. 



'5'' F. Schlenk, in The P^nzymcs, Vol. 2, Part 1, p. 255. Academic Press, New York, 

 1951. 



