48i 



Pyridines 



0*-P— OH 



0<-P— OH 



The fact that alcohol and lactic acid dehydrogenases all 

 have been found to contain 2 or 4 DPN molecules has also 

 inspired the hypothesis that hydrogen transfer might re- 

 quire a pair of adjoining prosthetic groups in a scheme 

 such as : 



in which a deuterated substrate is shown for clarity.* A 

 more detailed discussion has been pubUshed of the stereo- 



^ Jan van Eys, Anthony San Pietro and Nathan O. Kaplan, Science 

 127 1443 (1958). 



