Nicotinamide Nucleotide Enzymes 



FRITZ SCHLENK 



School of Medicine, University of Texas 



REPORTS OF INVESTIGATIONS in the field of the nicotinamide nu- 

 ^ cleotide enzymes are now so numerous as to make impossible 

 a complete review of the subject here; and in any case it would seem 

 to be unnecessary in view of the comprehensive articles that have 

 been published in recent years (la-k). Emphasis will therefore be 

 laid upon those details that have not been extensively discussed in 

 previous articles and to report some recent advances. 



CODEHYDROGENASE I AND II 



Of the two coenzymes in this group, codehydrogenase I (cozymase, 

 diphosphopyridine nucleotide, Co I), was detected in 1906 by 

 Harden as a coenzyme of alcoholic fermentation (2). The other, 

 codehydrogenase II (triphosphopyridine nucleotide, Co II), was dis- 

 covered in 1932 by Warburg (3). In a series of investigations by the 

 von Euler school (1921-34) methods for the purification and deter- 

 mination of cozymase were elaborated. Its classification as a nu- 

 cleotide was ascertained, its codehydrogenase nature was pro- 

 pounded, and the numerous reports denying its existence were 

 refuted (le, f). In 1934 the most noteworthy discovery in the field 

 was made: Warburg and Christian isolated nicotinamide from co- 

 dehydrogenase II (4) and demonstrated its function as part of a 

 hydrogen-transporting coenzyme (5). In 1935 nicotinamide was 

 isolated also from cozymase (6), and soon the very close relationship 

 between these two coenzymes was established by the work of the 

 institutes in Berlin and Stockholm. 



Both coenzymes are nicotinamide-adenine dinucleotides, the only 

 difference between them being that codehydrogenase II contains 

 three molecules, and codehydrogenase I two molecules, of phosphoric 

 acid. Later the transformation of one coenzyme into the other was 

 achieved by enzymatic dephosphorylation of codehydrogenase II 

 and enzymatic as well as chemical phosphorylation of codehydro- 

 genase I (7). The yield of codehydrogenase II by this reaction is, 

 however, rather low; the isolation from red blood cells is still the 



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