Pfizer Handbook of Microbial Metabolites 480 



CH3CH2OH ;=i CH3CHO (in yeast) 

 R— CHO ^ R— COOH (in yeast) 

 Glutathione — SH ;^ Glutathione — S — S — Glutathione (in yeast) 

 Isocitrate :?^ Oxalosuccinate (bacteria, yeast) 

 D-Glucopyranose-6-phosphate :?^ 6-Phospho-D-gluconolactone (yeast) 



L-GIutamate ;=i a-Ketoglutarate + NH4 (bacteria) 

 D-Glyceraldehyde-3-phosphate + Phosphate ;=i D-l,3-Diphosphoglyceric 



Acid (yeast) 



Some of these reactions occur quite generally. Oc- 

 casionally DPN and TPN are interchangeable, although 

 one or the other is used more efficiently. 



Direct transfer of hydrogen between the substrate and 

 the 4-position of the nicotinamide moiety of DPN (in the 

 presence of yeast alcohol dehydrogenase) has been dem- 

 onstrated, and the stereochemistry of this reaction studied 

 in exquisite detail by means of deuterated substrate : ^ ® 



In the second equation the deuterium atom is removed 

 exclusively, leaving deuterium-free DPN. This indicates 

 a marked- steric effect, since the deuterium atom projects 

 from one side of the molecule. Moreover, a single stereo- 

 isomer of deuterated ethanol is produced. 



Speculations have been made concerning the precise 

 nature of the coenzyme-apoenzyme-substrate-metal ion 

 complex. One model' is shown below: 



^ Harvey F. Fisher, Eric E. Conn, Birgit Vennesland and F. H. 

 Westheimer, J. Biol. Chem. 202 687 (1953). 



^ H. Richard Levy, Frank A. Loewus and Birgit Vennesland, J. Am. 

 Chem. Soc. 79 2949 (1957). 



^Kurt Wallenfels and Horst Sund, Biochem. Z. 329 59 (1957). 



