Distribution of transaminases in rat organs.

The rale which the transamination reaction plays in the metabolism of amino acids is not known exactly. The reaction was at first considered to be general and to involve most amino acids (1). However, results obtained in various laboratories suggested that transamination took place only with glutamic acid, aspartic acid, and alanine, and in a few cases with other amino acids (2-4). The development of accurate and specific methods for the analysis of amino acids permitted a revision of the problem, and today there are many reports which indicate that transamination is a reaction of wide scope, involving many acids. Feldman and Gunsalus (5) reported the occurrence of a wide variety of transaminases in bacteria. Hird and Rowsell (6) demonstrated that the insoluble particles of rat liver possess the ability to synthesize phenylalanine, tyrosine, and alanine from the corresponding keto acids and glutamic acid. The extensive work of Cohen indicated at first that transaminations are limited to a few amino acids, but recently Cammarata and Cohen (7) reported that enzyme preparations from liver, kidney, and heart are able to transaminate many amino acids. It was difficult to ascribe a rBle to the transamination reaction in the light of previous studies, since it was considered to be a reaction of limited scope. The present work was conducted for the purpose of determining quantitatively by paper chromatography the transamination reaction in various organs of the rat and to determine the number of amino acids involved in the reaction. As it will be shown, our results point clearly to the existence of multiple transaminating activities in all organs investigated. Furthermore, from the different ratios of activity among the organs investigated, it appears that more than one enzyme must be involved in the reaction. cY-Ketoglutaric and pyruvic acids were the only or-keto acids used in this investigation.