ASPARTASE 163 



any or all of the following products : ammonia, fumaric acid, 

 succinic acid, malic acid. 



HOOC.CH2.CH0.COOH 



Succinic // dehydrofieiiase 



Aspartase yf 



HOOC.CH0.CHNH2.COOH F=^ HOOC.CH=CH.COOH + NH3 



HOOC.CH^.rHOH.OOOH 

 Aspartase is found in many facultative anaerobes but is not, 

 apparently, involved in the reductive deamination of aspartic 

 acid to succinic acid by certain strict aerobes (as above). 



When cell preparations of aspartase are left to stand on the 

 bench, especially if the j^H is adjusted to around 4-0, the 

 activity steadily declines. The lost activity can be restored 

 if biotin is added to the cell suspension, which suggests that a 

 biotin-containing coenzyme is involved in aspartase action. 

 However, adenylic acid can also restore the lost activity but 

 much larger concentrations are required. The cell-free 

 aspartase has now been resolved into specific protein and 

 coenzyme portions, and the protein can be activated by the 

 addition of both adenylic acid and biotin, neither being active 

 alone. It is probable that adenyUc acid and biotin combine, 

 in the presence of an enzyme contained in the preparation, 

 to form a complex active as co-aspartase. 



A further example of desaturation deamination is the 

 breakdown of histidine by Esch. coli to give urocanic acid, 

 so called since it was first isolated from the urine of dogs. 

 HC=C— CH2.CHNH2.COOH HC=C— CH=CH.COOH 



HN N HN N +NH3 



\^ \^ 



CH CH 



Hydrolytic deamination 



A method of deamination that is theoretically possible 

 involves hydrolysis to the correspondiug hydroxy-acid : 



R . CHNH2 . COOH + H2O > R . CHOH . COOH + NH3 



