166 LIGHT AND LIFE 



The 300-400 vifx Region 



Harbury et al. (10) observed that the ability of a solvent to form 

 hydrogen bonds with 3-methyl lumiflavin has the most pronounced 

 influence on the position of the secondary flavin band in the near 

 ultraviolet. Hydrogen-bonding solvents tend to shift this band toward 

 370 m^, whereas solvents which are unable to form hydrogen bonds 

 shift it toward 330 m^u,. It is of particular interest here that a flavin- 

 peptide fragment which Kearney (11) obtained from digests of 

 succinic dehydrogenase also shows a shift of the secondary flavin 

 peak from 375 to 350 m^. 



Strittmatter (20) showed that the complex of DPNH cytochrome 

 reductase of liver microsomes with its substrate DPNH has a distinct 

 band at 315 m^. Although Strittmatter attributes this band mainly 

 to an interaction of the nicotinamide ring and the isoalloxazine ring 

 system of the reactants, he has also presented evidence that the adenine 

 moiety of the substrate is involved in enzyme-substrate binding. It 

 is therefore of interest that a band in the same spectral region is 

 found (3) when crotonyl CoA is added to the yellow form (17) of 

 butyryl dehydrogenase. As mentioned above, the butyryl dehydro- 

 genase-crotonyl CoA complex is also characterized by bands at about 

 420 xwjx and at 470 m^. When, however, the analog of crotonyl CoA, 

 crotonyl thioethylamine, which lacks the nucleotide moiety of CoA, 

 is added to the same enzyme, only the bands at 420 and 470-480 m^ 

 appear, and not that at 315 niyu,. In the case of the yellow form of 

 butyryl dehydrogenase, at least, we may therefore assign the 315 niju, 

 band to an interaction of the isoalloxazine ring system with a nucleo- 

 tide, and the 420 ni/x and 470-480 niyn bands to the interaction of 

 flavin with the non-nucleotide moiety of the substrate. The double 

 bond contained in the crotonyl moiety of the substrate may be neces- 

 sary for the appearance of this latter band. 



The 500-1000 )n,x Region 



A new absorption band in the 600-800 m^ region has only been foimd 

 with two flavoproteins thus far. These proteins are of deep green 

 color. Butyryl dehydrogenase, as isolated from beef and pig liver 

 or beef heart, shows this peculiarity (17, 3, 13) ; and the old yellow 

 enzyme of yeast coidd be transformed into a green-colored protein 

 on treatment with ammonium sulfate at pH 10 (14) . This trans- 

 formation of the old yellow enzyme appears to be reversible, whereas 

 the green form of butyryl dehydrogenase could never be produced 

 artificially. The green butyryl dehydrogenase can be converted, how- 



