584 BIOTIN 



buffer and dilute KCl solutions, addition of hiotin increases the deamina- 

 tion of aspartic acid.^^ 



The interdependence of biotin and adenylic acid during "aging" of fjac- 

 terial cells may be expressed by the following hypothetical scheme." 



Biotin + adenylic acid »■ Coenzyme form 



Enzyme-destroying Enzyme-destroying 



biotin adenylic acid 



4. Biotin in Other Enzyme Systems 



The decarboxylation of succinic acid to propionic acid appears to recjuire 

 the presence of biotin. ^°' ^^ In a biotin-defieient medium the production 



CO OH 

 CH2 

 CH, 

 COOH 



COOH 



I 

 -CO2 



CHo 

 CHs 



of carbon dioxide from added succinate is reduced and may be enhanced 

 by biotin. 



The metabolism of succinic acid is further linked with biotin through 

 the succinic acid dehydrogenase. The activity of this enzyme is appre- 

 cialily impaired in a cell-free extract of E. coli A\hich has been dialyzed 

 against phosphate buffer and dilute KCl solution. Full activity is restored 

 by the addition of biotin. ^^ 



Biotin may also be related to amino acid oxidases, and thus in further 

 consequence perhaps to protein synthesis. Both d- and L-amino acid oxi- 

 dases are formed by suitable strains of Neurospora crassa in a synthelic 

 medium containing 0.25 7 of biotin per liter. By increasing the concenti'a- 

 tion of biotin to 5 7 per liter the production of L-amino acid oxidase is 

 suppressed and that of D-amino acid oxidase is maintained. ^- 



The difficult enzymatic interrelationship between biotin and oleic acid 

 has already been discussed (p. 504). Its detailed mechanism has not yet 

 been elucidated. 



50 E. A. Delwiche, J. Bartcriol. 59, 439 (1950). 



5' H. C. Lichtstein, J. Bacieriol. 60, 4cS5 (1950). 



" A. E. Bender, H. A. Krebs, and N. II. Horowitz, Biochcm. J. 45, xxi (1949). 



