INTERACTIONS IN PYRIDINE NUCLEOTIDES^ 



Sidney Shifrin and Nathan O. Kaplan 



Graduate Department of Biochemistry 

 Brandeis University, Waltham, Massachusetts 



The essentiality of specific functional groups in the diphospho- 

 pyridine nucleotide (DPN) molecule for biological activity has been 

 studied by the use of coenzyme analogues in a large number of enzyme 

 systems (2, 8, 11, 21, 22). The usefulness of the coenzyme analogues 

 in studying intramolecular interactions in the pyridine nucleotides 

 will be presented in this report. 



Weber (24, 25) has studied the interaction of the adenine and 

 dihydronicotinamide moieties of DPNH by polarization fluorescence 

 and by the ability of adenine to transfer excitation energy to the 

 fluorescent dihydronicotinamide moiety. From such studies, Weber 

 (25) has suggested that there must be a strong force holding the 

 two moieties of the dinucleotide in a position which facilitates inter- 

 action. The configurational requirements, as well as the nature of 

 the forces facilitating intramolecidar interactions, have been studied 

 by the use of isomers as well as analogues of DPNH. 



Kaplan et al. (12) reported the isolation of a compound from a 

 "purified" DPN preparation which was identical with the biologi- 

 cally active coenzyme in its chemical analysis but differed from it 

 in enzymatic and spectral properties. This nucleotide was identified 

 as the alpha isomer of DPN; the compound is different from the 

 enzymatically active coenzyme in the configuration at the nicotinamide 

 ribose linkage. The enzymatically active DPN has a beta glycosidic 

 linkage at this point, and both isomers contain the beta adenylic 

 acid moiety. Table 1 compares the characteristics of DPN and the 

 isolated material. 



Examination of the chemically reduced a isomer for fluorescence 

 properties revealed that the energy of emission was maximum at 465 



' 1 his is publiiatioii No. (il ol the (.railiialc DtparliuciU ol Bicx liciiiistiy, 

 Hiandcis lliiivcisiiv. Wallhani. Massachusclts. This work, has been supported by 

 grams from the Naiioiiai Iiislitutes ol Heahh (NIH CV .'^(ill) and ihe National 

 Science Foundation (NSF (1-4512). 



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