FRANK M. HUENNEKENS 



by microbiological assay of its vitamin form or specific enzy- 

 matic assay of the denaturated preparation, and to be concen- 

 trated in a parallel fashion with the enzyme. In other cases, the 

 highly purified enzyme may exhibit an absorption spectrum 

 indicative of the bound coenzyme, and, as in the case of certain 

 flavoproteins, a change in the absorption spectrum (i.e., cor- 

 responding to reduction of the flavin) may occur upon addition 

 of the appropriate substrate. 



By one or another of the techniques just described, the 

 series of coenzymes listed in Table I have been established. 



TABLE I 



Function of Coenzymes 



Coenzyme 



Group transferred 



Diphosphopyridine nucleotide 

 Triphosphopyridine nucleotide 

 Flavin adenine dinucleotide 

 Riboflavin phosphate 

 Lipoic acid 

 Coenzyme A 

 Diphosphothiamin 

 Pyridoxal phosphate 

 Tetrahydrofolic acid 

 iJ-Adenosyl methionine 

 Adenosine diphosphate (or 



monophosphate ) 

 Uridine diphosphate 

 Cytidine disphosphate 

 Guanosine diphosphate 



Hydrogen ions and electrons 



Hydrogen ions and electrons 



Hydrogen ions and electrons 



Hydrogen ions and electrons 



Hydrogen ions and electrons; acyl 



Acyl 



Aldehyde ; carbonyl 



Amino 



Formyl (hydroxymethyl) 



Methyl 



Acyl 

 Sugar 

 Choline 

 Phosphate 



Inspection of the table reveals several items of interest. First, 

 all of the coenzymes participate in group transfer reactions, which 

 may be represented in the general case by the following equa- 

 tions : 



(1) 



X + D - G 



A + X - G 



^ X - G + D 



-^ A - G + X 



(2) 



where X is the coenzyme, D — G, the donor with group G to be 



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