94 



growth: synthesis op bacterial protoplasm 



the original work, other investigators have obtained cell-free 

 preparations of transaminating enzymes, and these appear to 

 catalyse, m vitro, transamination between glutamic acid and 

 oxalacetic acid or between glutamic acid and pyruvic acid, but 

 not to carry out a general transamination as first suggested. 



COOH 



COOH 



CH2 COOH 



I I 



CHg + CHg 



I I 



CHNHa C=0 



I I 



COOH COOH 



Glutamic Oxalacetic 



COOH 



CH2 COOH 



I I 



CH2 + CH2 



I I 



C=0 CHNH2 



I I 



COOH COOH 



a-ketoglutaric Aspartic 



COOH 



CH, 



CH, 



CHo 



CK 



CH2 



I 

 CHNH2 



I 

 COOH 



Glutamic 



+ c=o 



COOH 



Pyruvic 



CH2 + CHNH2 



I I 



C=0 COOH 



I 

 COOH 



a-ketoglutaric Alanine 



The only " new " amino-acid formed in this way is alanine 

 from pyruvic acid. The prosthetic group of transaminase is 

 pyridoxal phosphate and if an organism has lost the ability to 

 synthesise pyridoxin (see p. 33) then it cannot produce 

 active transaminase. Recent work with Lactobacilli, which 

 have lost the abihty to synthesise pyridoxin, has shown that the 

 organisms can grow in a medium which contains D-alanine 

 even in the absence of pyridoxin. Organisms grown in this 

 medium are devoid of pyridoxin and its derivatives, whereas 

 organisms grown in media containing pyridoxin but no 



