Reductive amination by recombinant Escherichia coli: Whole cell biotransformation of 2-keto-3-methylvalerate to l-isoleucine

Transaminases and their Applications

“…3-Fluoropyruvate + methylbenzylamine [47] l-Homoalanine Pyruvate + (rac)-β-amino-N-butyric acid KR [52] l-Isoleucine l-Alanine TA 2-Keto-3-methyl-valerate + l-alanine AS [53] the correct conformation has to be produced. Recently, the asymmetric synthesis of prochiral diketones to 3-substituted cyclohexylamine derivatives serving as a build ing block for the multidrug-resistant protein MRP1 has been introduced [58].…”

Whole cell biotransformation for reductive amination reactions

“…28 In order to investigate the metabolic redox capacity of recombinant E. coli for asymmetric styrene epoxidation deletion, mutants lacking genes relevant for the NADH regeneration were compared in silico and in vivo according to NADH regeneration rates. 13 Based on this approach, several genes that are directly involved in NADH regeneration were selected to assess their potential to increase reductive amination of 2-keto-3-methylvalerate to l-isoleucine 16 (Fig. 2C).…”

“…1F) by metabolically active E. coli cells to synthesize l-isoleucine from 2-keto-3-methyvalerate. 16 …”

“…Amino acid dehydrogenases may be coupled with transaminases to enable reductive amination of many keto acids. For example, we have described an E. coli whole cell biotransformation system for reductive amination of 2-keto-3-methylvalerate (KMV) to the amino acid l-isoleucine 16 by coupling endogenous l-alanine dependent transaminase AvtA with NADH-dependent l-alanine dehydrogenase from B. subtilis. Recycling of the cofactor NADH was ensured by glucose catabolism of the host E. coli.…”

“…Both the non-natural keto acid or the non-natural amino acid may be toxic to the reductive amination host cell as observed for the keto acids ketoisocaproate and ketoisovalerate, 16 therefore, use of alternative hosts such as C. glutamicum or Pseudomonas may be needed. Moreover, uptake of the nonnatural keto acid into the host cell and export of the produced non-natural amino acid out of the cell may slow or even preclude effective reductive amination and may necessitate using alternative hosts or co-expression of transport genes.…”