The reductive amination of α-ketoisocaproic acid using a leucine dehydrogenase-modified gold electrode

ABSTRACTIn the present paper, the reductive amination of α-ketoisocaproic acid to L-leucine was monitored using a new modified electrode based on gold nanoparticles (AuNPs) and leucine dehydrogenase (LeuDH). The modified electrode was prepared by self-assembling of AuNPs with thiocytosine followed by the immobilization of the enzyme. The enzyme-modified electrode response was investigated by chronoamperometry for indirect quantification of ammonium ion () involved in the reaction. This reaction is catalyzed by LeuDH and takes place in the presence of ammonium chloride, as nitrogen source, and nicotinamide adenine dinucleotide (NADH), as cofactor. The enzyme-modified electrode was also used for in situ electrochemical NADH regeneration. After one step NADH regeneration the conversion of ammonium ion was improved. The modified electrode has good sensitivity (0.91 × 10−3 A/M) and reproducibility with an RSD of 8.4% (n = 4). The experimental determination of ammonium ion was confirmed by standard Berthelot sp...