STICKLAND REACTION 167 



2CH2NH2.COOH + CH3.CHNH2.COOH + 2H2O 



= 3CH3.COOH + 3NH3 + CO2. 



This oxido -reduction reaction between two amino-acids, 

 usually called the " Stickland reaction," would seem to be 

 specific for certain Clostridia such as CI. sforogenes and CI. 

 botulinum, but is not carried out by all Clostridia. Other 

 members of the genus employ a different method of deamina- 

 tion in which single amino-acids are attacked with the 

 liberation of ammonia and gaseous hydrogen. The growth of 

 certain Clostridia on meat media results in the formation of 

 considerable volumes of gas, hence the name " gas gangrene " 

 given to the clinical condition following the infection of 

 wounds with certain pathogenic Clostridia. The greater part 

 of this gas is liberated during the deamination of certain 

 amino-acids. For example, CI. tetmiomorphum attacks tyro- 

 sine and histidine with the liberation of hydrogen and ammonia. 

 In most cases the products of the deamination have not been 

 fully identified and we do not know how the hydrogen is 

 formed during the deamination process, but it has been 

 suggested that we have here a form of oxidative deamination, 

 consisting of dehydrogenation followed by release of the 

 hydrogen as molecular hydrogen instead of combination 

 with a H-acceptor. 



DECARBOXYLATION 



The removal of the terminal — COOH group of an amino- 

 acid is carried out by specific amino-acid decarboxylases 

 with the formation of the corresponding amine : 



R . CHNH2 . COOH > R . CH2NH2 -f CO2. 



The decarboxylases are specific for the natural isomer of one 

 amino-acid. From studies of these enzymes in a cell-free 

 state, it seems that only such amino-acids are attacked as 

 have at least one chemically active (polar) group in the 

 molecule other than the terminal — COOH and the a-NHg 

 groups. Thus decarboxylases have been described for 

 arginine, lysine, ornithine, histidine, tyrosine, glutamic acid, 



