D. E. GREEN 



acts as the transforming agent by combining two physiological func- 

 tions. In the same way, visual purple becomes a vehicle for trans- 

 forming light energy into chemical energy and, we must assume, 

 eventually reacts in some way with nervous elements of the retina. 

 Instances of enzymes with multiple functions and multiple active 

 groups have been known in the literature, but the tendency hitherto 

 has been to regard them as biological curiosities. Thus pyruvic 

 oxidase of Lactobacillus delbrueckii contains two prosthetic groups, viz- 

 flavin dinucleotide and diphosphothiamin. Milk flavoprotein con- 

 tains two prosthetic groups (flavin dinucleotide and another as yet 

 unidentified) and catalyzes the oxidation of purines, aldehydes, and 

 dihydrocoenzyme I. The /-amino acid oxidase of rat kidney has two 

 enzymic functions. These enzymes with multifunctions may be in- 

 volved in the transfer of chemical energy from exergonic to endergonic 

 processes. In other words, enzymes may ultimately turn out to be the 

 energy transformers and converters of the cell. 



References 



(1) Elvehjem, C. A., Madden, R. J., Strong, F. M., and Woolley, D. W., 

 J. Am. Chem. Soc, 59, 1767 (1937). 



(2) Fildes, P., Lancet, I, 955 (1940). 



(3) Green, D. E., Advances in Enzymology, Vol. I. Interscience, New York, 

 1941, p. 177. 



(4) Harden, A., and Young, W. J., Proc. Roy. Soc. London, B77, 405 (1906). 



(5) Schoenheimer, R., The Dynamic State oj Body Constituents. Harvard Univ. 

 Press, Cambridge, 1942. 



(6) Woods, D. D., Brit. J. Exptl. Path., 21, 74 (1940). 



(7) Woolley, D. W., Science, 100, 579 (1945). 



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