582 



BIOTIN 



3. BioTiN IN Deamination 



The possibility that deamination may play a part in the metabolic inter- 

 relation of aspartic acid and oxalacetic acid'-^ has been already mentioned 

 (p. 576), and it has been made further probable by the finding that in aging 

 bacterial cells the deamination of aspartic acid is markedly impaired and 

 may be restored by the addition of biotin. Similar observations were made 

 on the deamination of serine and threonine."** Table IX contains some of 

 the pertinent data.^^- ** 



TABLE IX 

 Biotin Activation of Deaminases 



In the deamination of serine or threonine, first water is removed with 

 the formation of the imino acid, leading in turn to the corresponding keto 

 acid, in the case of serine to pyruvic acid.-^ The reaction is not reversible. 



CHjOH 

 CHNHj 



COOH 



Serine 



-H2O 



C-NH, 



COOH 



a-Amino acrylate 



CH2 



I 

 C=KH 



I 

 COOH 



Iminopyruvate 



+ H:0 



CH, 



C=0 



I 

 COOH 



Pyruvate 



The deamination of aspartic acid may proceed through fumarate to 

 malate or to succinate according to the following scheme. 



■"• H. C. Lichtstein and W. W. Umbreit, J. Biol. Chcm. 170, 423 (1947). 



i 



