IV. BIOCHEMICAL SYSTEMS 495 



Oxalacetic acid — malic acid (DPN) 

 Oxalosuccinic acid — isocitric acid (DPN) 

 /3-Hydroxybutyric acid — ^acetoacetic acid (DPN) 

 a-Ketoglutarate — ^isocitric acid (TPN) 



3. Acyl phosphate :;=^ Aldehyde- 1 -phosphate 



1,3-Diphosphoglyceric acid — 3-phosphoglyceraldehyde (DPN) 



4. Acid ;;:± Aldehyde (hydrate) 



Gluconic acid— glucose (DPN) (TPN) 

 6-Phosphogluconic acid — glucose-6-phosphatc (TPN) 

 Phosphoglyceric acid — phosphoglyceraldehyde (DPN) 

 Phosphogluconic acid — ribulose phosphate (TPN) 

 Acetic acid — acetaldehyde (DPN) 



5. Imine ^ Amine 



Iminoglutaric acid — L-glutamic acid (DPN-TPN)'*^^ 



6. Miscellaneous 



Reduction of nitrate to nitrite^^ 



The oxidation of liciferin to produce bioluminescence^'* 



Dehydration of formic acid^^- ^^ 



HCOOH + DPN -^ CO2 + DPNH2 

 Conversion of choline to betaine (DPN)^^-^^ 

 Conversion of vitamin Ai to rhodopsin (DPN)^^ 

 Reduction of methemoglobin (DPN)i'^° 

 Destruction of testosterone by liver mince (DPN)^°' 

 L-a-Glycerophosphate to dihydroxyacetone phosphate^ "^ 

 Dismutation of pyruvate (in bacterial extracts) ^^^ 



Pyruvate -f phosphate -f- DPN -^ Acetyl phosphate + 

 CO2 + DPNH; Pyruvate -f DPNH -^ Lactate -j- DPN 



I. SYSTEMS 



The biochemical reactions listed previously do not occur independently 

 but as a part of a series of reactions by which an organism carries out the 



82a The glutamic acid dehydrogenase system of yeast and bacteria must be coupled 

 with TPN, although the corresponding system in animal tissues is non-specific 

 in its DPN -TPN preference. 



" R. Adler and M. Srenwasaya, Hoppe-Seyler's Z. physiol. Chem. 249, 24 (1937). 



s* F. H. Johnson and H. Eyring, /. Am. Chem. Soc. 66, 848 (1944). 



"J. C. Wirth and F. F. Nord, Arch. Biochem. 1, 143 (1942). 



96 P. J. G. Mann and J. H. Quastel, Biochem. J. 31, 869 (1937). 



" J. R. Klein and P. Handler, /. Biol. Chem. 144, 537 (1942). 



98 J. N. Williams, Jr., /. Biol. Chem. 195, 37 (1952). 



99 R. Hubbard and G. Wald, Science 115, 60 (1952). 



lo" H. R. Gutman, B. J. Jandorf, and O. Bodansky, J. Biol. Chem. 169, 145 (1947). 



i»i M. L. Sweat and L. T. Samuels, /. Biol. Chem. 173, 433 (1948). 



102 T. Baranowski, J. Biol. Chcju.lSO, 535 (1949). 



193 S. Korkes, J. R. Stern, I. C. Gunsalus, and S. Ochoa, Nature 166, 439 (1950). 



