Spectrophotometric detection of histidine and lysine using combined enzymatic reactions

An amino acid-sensing system with absorption spectrophotometric detection was developed. To ensure specific recognition of each amino acid, aminoacyl-tRNA synthetases were employed and the concentration of NADH produced by way of several enzymatic reactions was measured. Using this detection system, from 1.5 to 55 μM of histidine and from 15 to 95 μM of lysine could be measured selectively in HEPES-KOH buffer (pH 8.0).