Enzymatic Synthesis of Biologically Active -Phosphinic Analogue of α-Ketoglutarate.

Amino acid analogues with a phosphorus-containing moiety replacing the carboxylic group are promising sources of biologically active compounds. The -phosphinic group, with hydrogen-phosphorus-carbon (H-P-C) bonds and a flattened tetrahedral configuration, is a bioisostere of the carboxylic group. Consequently, amino--phosphinic acids undergo substrate-like enzymatic transformations, leading to new biologically active metabolites. Previous studies employing NMR-based metabolomic and proteomic analyses show that in , α-KG-γ-P (the distal -phosphinic analogue of α-ketoglutarate) can be converted into -Glu-γ-P. Notably, α-KG-γ-P and -Glu-γ-P are antibacterial compounds, but their intracellular targets only partially overlap. -Glu-γ-P is known to be a substrate of aspartate transaminase and glutamate decarboxylase, but its substrate properties with NAD-dependent glutamate dehydrogenase (GDH) have never been investigated. Compounds containing bonds are strong reducing agents; therefore, enzymatic NAD-dependent oxidation is not self-evident. Herein, we demonstrate that -Glu-γ-P is a substrate of eukaryotic GDH and that the pH optimum of -Glu-γ-P NAD-dependent oxidative deamination is shifted to a slightly alkaline pH range compared to -glutamate. By P NMR, we observe that α-KG-γ-P exists in a pH-dependent equilibrium of keto and germinal diol forms. Furthermore, the stereospecific enzymatic synthesis of α-KG-γ-P from -Glu-γ-P using GDH is a possible route for its bio-based synthesis.