340 



RIBOFLAVIN 



Since homogeneous preparations contain 0.66% riboflavin phosphate, 

 and since ultracentrifuge measurements of the molecular weight give a 

 figure^^ of about 70,000, there can be only one molecule of prosthetic ribo- 

 flavin phosphate per molecule of flavoprotein. Elementary analysis of the 

 enzyme by TheorelP^ yields typical figures for a protein: C = 51.5%; 

 H = 7.37%; N = 15.9%; P = 0.043%; S = 1.0%. The specific rotation, 

 [a] „ is -30°. 



TABLE I 

 Flavopkoteins 



° RP = riboflavin phosphate; FAD = flavin adenine dinucleotide. 

 * M.B. = Methylene blue. 



Kuhn and Desnuelle^^"^" obtained results which were approximately the 

 same except that they found 0.48% sulfur instead of 1.0%. Hydrolysis of 

 the apoenzyme by boiling with dilute sulfuric acid and analyses of the 

 resulting hydrolyzate for amino acids gave the following values: arginine 



2« R. A. Kekwick and K. O. Pedersen, Biochem. J. 30, 2201 (1936). 



" H. Theorell, Biochem. Z. 290, 293 (1937). 



28 R. Kuhu and P. Desnuelle, Bcr. 70, 1907 (1937). 



2^ R. Kuhn and 1'. Desnuelle, Z. physiol. Cliem. 251, 14 (1938). 



=•« R. Kuhn and P. Desnuelle, Z. physiol. Chem. 251, 19 (1938). 



