NITROGEN METABOLISM 231 



C. With One Carbon Atom Less. 

 (a) Aldehydes, 



R.CHo.CO.COOH > R.CH2.CHO + COo. 



The aldehydes are usually not end products since they 

 undergo further reactions : — 



(6) Saturated Acids, 



oxidation 

 R.CHo.CHO > R.CH2.COOH. 



The aldehyde is oxidised to give substituted acetic acids, 

 particularly by bacteria under aerobic conditions. For 

 example, phenylalanine gives phenyl-acetic acid : — 



(c) Saturated Alcohols, 



reduction 

 R.CHo.CHO > R.CH2.CH2.OH. 



This type of breakdown of amino -acids is very common 

 among the yeasts, and is, in fact, the mode of origin of 

 the higher alcohols which constitute the fusel oil produced 

 during alcoholic fermentation, as was shown by Ehrlich. 

 Fungi, Proteus, and the lactic acid bacteria can also 

 bring about this type of change. As examples may be 

 mentioned the formation of /50-amyl alcohol from 

 leucine : — 



CH3 CH3 



\ \ 



^CH.CHa.CH.NHo.COOH > ^CH.CH2.CH2.0H. 



/ / 



CH3 CH3 



(Leucine) (jso-amyl alcohol) 



Tyrosine gives tyrosol (p-hydroxyphenyl -ethyl alcohol), 

 h:o<; y('H...{'Hj)]i, and tiyptophane gives tryptophol 



IG 



