372 IMMUNO-CATALYSIS 



(Cozymase-I^reduced Cozymase). The enzyme is inhibited 

 by iodoacetate. 



(23) In bacteria, pyruvic acid can undergo dismutation yielding 

 lactic and acetic acids (Lipmann, 1939; Krebs, 1937). Ac- 

 cording to Lipmann, the reaction requires cocarboxylase, 

 flavine-adeninedinucleotide, Mg"^ + , Mn+ + , or Co+ + , in- 

 organic phosphate and protein(s). 



(24) The decarboxylation of pyruvate by means of hydrogen perox- 

 ide to acetic acid, water and carbon dioxide occurs in pneu- 

 mococci (Sevag, 1933) and certain other bacteria. Hydrogen 

 peroxide is formed from the aerobic oxidation of glucose, 

 lactate, etc. in these bacteria. (For further information see 

 Sumner and Somers, 1947.) 



3, Tricarboxylic Acid Cycle"^ 



From the standpoint of the synthesis of amino acids, and therefore 

 of proteins, pyruvic acid would seem to be the most critical a-keto acid 

 as the starting point. The following reactions (p. 373) are given to 

 show how higher a-keto acids can be derived from pyruvic acid. 

 (For the factors involved in the above reactions, see Werkman and 

 Wood, 1942; Lipmann, 1941; Barron, 1943; Krebs, 1943; Sumner 

 and Somers, 1947; Baldwin, 1947; Gurin, 1948). 



4. Synthesis of Amino Acids From «-Keto Acids 



a. Oxidative Deamination of Amino Acids. Two principal types 

 of reactions are responsible for the synthesis of amino acids. The 

 synthesis of amino acids can take place by reversible amination of 

 a-keto acids derived from the intermediary products of carbohydrate 

 metabolism, and from the oxidative deamination of amino acids as 

 indicated below: 

 HOOCCH2CH2CH(NHJCOOH+ViO,^ 



" HOOCCH2CH2COCOOH4-NH3 

 1 ( -|- )-glutamic acid a-ketoglutaric acid 



The enzyme which catalyzes this reaction is known as glutamic 

 dehydrogenase and is found in yeast, plants, bacteria and animals. 

 Euler, ei ah (1938) and Dewan (1938) found this enzyme in liver, 



*Or Krebs' citric acid cycle has been undergoing, with respect to the sequence of 



