680 THE BIOCHEMISTRY OF B VITAMINS 



Table 40. Competitive Inhibitors of Flavin-Adenine-Dinucleotide for 

 D- Amino Acid Oxidase 62 



. Quinine Equivalent* 



At 37° C At 30° C 



Auramine 7 



Atebrin 2.5 2 



Novalauramine 2 



Quinine 1 1 



Quinine methochloride 1 1 



6-Methoxyquinoline 1 1 



Plasmochin 1 



7-Chloro-4-(4-diethylamino-l-methylbutyl- 



amino)-2-methylquinoline 1 



7-Chloro-4- (4-diethylamino- 1-methylbutyl- 



amino)-3-methylquinoline 0.4 0.5 



7-Chloro-4- (4-diethylamino- 1-methylbutyl- 



amino)quinoline 0.5 0.5 



a-(Diamylaminomethyl)-l,2,3,4-tetrahydro- 



9-phenanthrenemethanol 

 Sulfathiazole 

 Sulfapyridine 

 Sulfadiazine 

 Sulfanilamide 

 Benzenesulfonamide 

 N- (4-Diethylamino- 1 -methylbutyl)-/3- 



(p-dimethylaminophenyl)alanine 

 Aniline 

 Pyridine 

 0L-a-(p-Dimethylaminophenyl)glycine 



* The ratio of concentrations of quinine and inhibitor required to give the same amount of inhibition at 

 any concentration of flavin-adenine-dinueleotide. 



active as quinine. The sulfonamides are considerably less effective. The 

 dissociation of the coenzyme from D-amino acid oxidase does not occur 

 readily at 30° C, but dissociation is readily detectable at 37° C. At the 

 latter temperature, the inhibitions resulting from quinine appear to be 

 reversible and competitive with the coenzyme. The dissociation constants 

 for two different enzyme preparations are 4.6 X 10 7 and 6.9 X 10 7 for the 

 enzyme complex and 4.6 X 1(H and 8.9 X 1(H for the quinine-apoenzyme 

 complex. With atebrin, two types of inhibition appear to exist. One is 



(CH 3 ) 2 — N+=< \=C— <f \-N(CH 3 ) 2 



ci : 7 X=/ I \=J 



NH 2 

 auramine 



C2H5 



NH— CH— CH 2 — CH,— CH 2 — N 



I \ 



CH 3 C 2 H 6 



plasmochin 



