212 A SYMPOSIUM ON RESPIRATORY ENZYMES 



appearance of glutamic acid was an adaptation of the Foreman (8) 

 method, which has recently been shown by Zorn (9) to be unreliable 

 for studying transamination. 



In contrast to certain of the above findings Cohen (10) found that 

 of twenty-one different alpha-amino acids studied in pigeon breast 

 muscle Z(— )-aspartic acid and Z( + )-alanine were the most active in 

 forming glutamic acid in the presence of alpha-ketoglutaric acid. 

 Alpha-aminobutyric acid and ?( + ) -valine were slightly active, but 

 none of the remaining amino acids was appreciably active. Of a 

 series of alpha-keto acids studied, oxalacetic and pyruvic acids were 

 the most active in causing the anaerobic disappearance of glutamic 

 acid. Alpha-ketobutyric and mesoxalic acids were slightly active, 

 but no activity was observed with alpha-ketovaleric, alpha-keto- 

 caproic, acetoacetic, and laevulic acids. Moreover, no transamination 

 was observed between alpha-ketoglutaric acid and a variety of 

 amino compounds other than alpha-amino acids. The formation and 

 disappearance of glutamic acid were determined by the method of 

 Cohen (11). The specificity and accuracy of this method has recently 

 been confirmed (12, 13). 



d-Amino Acids.— Amino acids of the d series are not active in 

 transamination (10, 14, 15, 16). Activity with (i-amino acids has been 

 reported by Braunstein (1), Braunstein and Azarkh (17), and Euler 

 et at. (18). 



Peptides.— The role of peptides as transamination substrates is of 

 considerable interest. As noted above, Braunstein and Kritzmann (7) 

 observed no activity with various peptides. In the case of trans- 

 aminase preparations Cohen (14) was unable to demonstrate any 

 appreciable transamination between glutathione and oxalacetic acid. 

 On the other hand Agren (19) reported that in minced cattle 

 diaphragm muscle transamination takes place between alpha- 

 ketoglutaric acid and the peptides glycylaminobenzoic acid and 

 valylglycine. Valylglycine was found to be as active as alanine 

 (about 30 per cent transamination), while glycylaminobenzoic acid 

 was less active. Agren employed the same method as Braunstein and 

 Kritzmann for measuring transamination. In view of the latter work- 

 ers' observation that glycine interfered with this detemiination (1) 

 by being carried down in the dicarboxylic acid amino nitrogen 

 fraction, it is possible that the results obtained by Agren with 

 glycine dipeptides are due to this fact. No control experiments of 

 glycine dipeptides plus tissue are reported. 



"Primary" and "Secondary" Substrates.— According to Braunstein 



