TRANSAMINATION 211 



The present review will deal chiefly with the system represented 

 by Reaction 1, and the use of the term "transamination" will be 

 Hmited to this reversible, enzyme-catalyzed system. 



Discovery of Transamination Reaction 



Transamination as a biological reaction was first recognized by 

 Needham "(3), who found that glutamic and aspartic acids disap- 

 peared anaerobically when added to pigeon breast muscle without 

 a decrease in amino nitrogen. She could find no increase in urea or 

 ammonia nitrogen, but did observe an increase of succinic acid. 

 She suggested that "possibly a combination of the amino group 

 with some reactive carbohydrate residue takes place; then when 

 splitting and oxidation occur the amino group is retained in the 

 form of a new amino acid." 



Unrecognized evidence for transamination was published from 

 Szent-Gyorgyi's laboratory in 1936 and 1937. It was observed that 

 the rate at which oxalacetic acid disappeared was greatly increased 

 when glutamic acid was added to pigeon breast muscle (4) and to 

 certain enzyme preparations from the same tissue (5). 



Credit for the discovery of transamination goes to Braunstein and 

 Kritzmann (6), who carried out the first detailed investigation of 

 this reaction. They succeeded in showing that the reaction, termed 

 "Umaminierung" by them, took place in pigeon breast muscle. The 

 system represented in Reaction 3 was studied, and they were able 

 to show its reversibility by isolation and chemical identification of 

 the alanine and glutamic acid formed. 

 (3) Z( + ) -glutamic acid -j- pyruvic acid <^ a-ketoglutaric acid -f Z(-j-) -alanine. 



Substrates Aciive in Transamination 



Investigations by Braunstein and Kritzmann (7) led them to con- 

 clude that the enzymatic transfer of amino groups in pigeon breast 

 muscle takes place between any alpha-amino acid (with the possible 

 exception of glycine) and the dicarboxylic acids, alpha-ketoglutaric 

 and oxalacetic, as well as between the dicarboxylic amino acids, 

 glutamic and aspartic, and various alpha-keto acids. No amino group 

 transfer was observed in the following systems: (1) between mono- 

 carboxylic alpha-amino acids and monocarboxylic alpha-keto acids; 

 (2) from amines and peptides; or (3) from alpha-amino dicarboxylic 

 acids to ketones, hydroxy-ketones, or aldehydes. The analytical 

 method employed in this study for measuring the formation or dis- 



