58 PHYSIOLOGY OF BACTERIA 



and then the hydroxy acid gave off CO2 and thus became 

 amyl alcohol. 



C4H9-CH(OH)-C02H = CO2 + C4H9-CH20H 



In a similar way, yeast can hydrolyze other amino acids 

 (see page 44). 



The de-aminization by reduction will be mentioned 

 on page 63 where the propionic acid bacteria reduced 

 aspartic acid to succinic acid. This process is very 

 probably not a source of energy. 



The third possibility, the de-aminization by oxidation, 

 has been used to explain the formation of succinic acid 

 by yeast. It was shown on page 43 that yeast does not 

 produce succinic acid from aspartic acid like the propionic 

 bacteria do, but from glutamic acid. It is, of course, 

 impossible to state whether the removal of NH3 is 

 accomplished by direct oxidation or by hydrolysis, 

 immediately followed by oxidation; the result is the 

 same. 



This type of oxidation process is also found with fungi. 

 Very probably it will yield energy. 



The last possibility of deaminization, the splitting 

 off of NH3 leaving an unsaturated carbon chain, seems 

 to have been observed only once, with histidine, though 

 performed by a number of species of the colon-aerogenes 

 group. Raistrick (1917) found the following decom- 

 position of histidine : 



(C3H3N2)-CH2-CH(NH2)-COOH = 



Histidine 



(C3H3N2)-CH:CH-COOH -1- NH3 



Urocanic acid 



Most probably, this process does not yield energy. 

 Perhaps, neurin is formed from lecithin by a similar 

 desaturation. 



