Recent trends and novel concepts in cofactor-dependent biotransformations

Abstract

Cofactor-dependent enzymes catalyze a broad range of synthetically useful transformations. However, the cofactor requirement also poses economic and practical challenges for the application of these biocatalysts. For three decades, considerable research effort has been devoted to the development of reliable in situ regeneration methods for the most commonly employed cofactors, particularly NADH and NADPH. Today, researchers can choose from a plethora of options, and oxidoreductases are routinely employed even on industrial scale. Nevertheless, more efficient cofactor regeneration methods are still being developed, with the aim of achieving better atom economy, simpler reaction setups, and higher productivities. Besides, cofactor dependence has been recognized as an opportunity to confer novel reactivity upon enzymes by engineering their cofactors, and to couple (redox) biotransformations in multi-enzyme cascade systems. These novel concepts will help to further establish cofactor-dependent biotransformations as an attractive option for the synthesis of biologically active compounds, chiral building blocks, and bio-based platform molecules.

Production of (S)-2-aminobutyric acid and (S)-2-aminobutanol in Saccharomyces cerevisiae

“…Threonine deaminases are pyridoxal-5′-phosphate (PLP) dependent, with the PLP co-factor remaining in the active site and being regenerated during the reaction cycle [49]. In S. cerevisiae PLP levels are elevated when the yeasts are grown under thiamine deficient conditions as the synthesis of PLP is inhibited by the presence of thiamine [50].…”

Engineering of alanine dehydrogenase from Bacillus subtilis for novel cofactor specificity

“…From an applied perspective, AADHs have the advantage of liberating the amino moiety as free ammonia or, in reverse direction, of directly incorporating ammonia into a keto acid. Furthermore, AADHs link deamination/amination to the reduction/oxidation of a nucleotide cofactor, which enables coupling to a variety of energy consuming/generating processes [5].…”

Hybrid C3N4/Fluorine‐Doped Tin Oxide Electrode Transfers Hydride for 1,4‐NADH Cofactor Regeneration

“…Literature shows that electrochemistry offers one of the best approaches for NADH regeneration, [3] and processes can easily be scaled up as they rely on a cheap electrical energy input. In contrast to enzymatically, chemically, or photochemically driven NAD + reduction, [2,4] electrically driven NADH regeneration does not need sacrificial electron donors (formate, phosphite, etc) or sacrificial hole scavengers (TEOA, EDTA, etc.). An electricity input, which could be supplied, for instance, by efficient perovskite solar cells, [5] drastically simplifies downstream processes (Scheme 1).…”

“…[2] The activated cofactor (reduced nicotinamide adenine dinucleotide phosphate, 1,4-NADH) is oxidized by the biocatalyst, which transfers one hydride equivalent (H À ) to the desired substrate. Owing to high costs of the hydride carrier, in situ regeneration of NADH is needed to develop economically attractive biotechnological transformations (see Scheme 1).…”

“…The Rh-C 3 N 4 @FTO electrode activity was calculated to be 0.0042 U/cm 2 (1 U being the enzymatic unit corresponding to 1 micromole of NADH produced per minute). As a comparison, productivity of NADH regeneration on bare FTO under the same conditions is 21 times lower.…”