Metabolism of aromatic amino acids by the rat heart and diaphragm

Abstract

1. Introduction Because incubation of [U-14~]phenylalanine or tyrosine with muscle preparations does not produce r4C02, it is assumed that these aromatic amino acids are poorly metabolised [l-3]. Release of aromatic amino acids from muscle preparations in the presence of cycloheximide has therefore been used as an index of muscle protein degradation. However, there is some evidence that aromatic amino acids may be at least transaminated by muscle [4,5]. This might inter- fere with methods of detection which are dependent upon the presence of an amino group, e.g., amino acid analysis or the amino acyl tRNA synthetase method [6]. Here, the transamination of aromatic amino acids by homogenates and whole tissue prepa- rations is reported. 2. Experimental Radiochemicals were from The Radiochemical Centre, Amersham HP7 9LL. Biochemicals and other chemicals were either from Sigma (London) Chemical Co., Poole BHI7 7NH, or BDH Chemicals, Poole BH 12 4NN. 2.2.