The Power of Biocatalysts for Highly Selective and Efficient Phosphorylation Reactions

Reactions involving the transfer of phosphorus-containing groups are of key importance for maintaining life, from biological cells, tissues and organs to plants, animals, humans, ecosystems and the whole planet earth. The sustainable utilization of the nonrenewable element phosphorus is of key importance for a balanced phosphorus cycle. Significant advances have been achieved in highly selective and efficient biocatalytic phosphorylation reactions, fundamental and applied aspects of phosphorylation biocatalysts, novel phosphorylation biocatalysts, discovery methodologies and tools, analytical and synthetic applications, useful phosphoryl donors and systems for their regeneration, reaction engineering, product recovery and purification. Biocatalytic phosphorylation reactions with complete conversion therefore provide an excellent reaction platform for valuable analytical and synthetic applications.

DiRect: Site-directed mutagenesis method for protein engineering by rational design

Site-directed mutagenesis (SDM), an indispensable method in molecular biology and protein engineering, is rather time-consuming and laborious. Protein engineering, especially that of enzymes, nowadays increasingly relies on rational design approaches in which both SDM and protein expression are the bottlenecks because they are generally based on the recombinant DNA technology. Here, we developed a new PCR-based mutagenesis method, DiRect, that achieves high performance in product quality (≥99% substitution) without recombinant DNA technology. We applied DiRect in combination with a cell-free protein expression system to an industrially relevant enzyme, nicotinamide adenine dinucleotide phosphate-dependent 3-quinuclidinone reductase from Rhodotorula rubra. In a single round of screening, 90 newly designed mutant proteins were produced within two days, and an unreported mutant (Q135I) exhibiting much higher thermostability than the wild-type enzyme was successfully identified within one extra day. Thus, DiRect is a simple, efficient, and potentially scalable SDM method.

Biocatalysis - Key enabling tools from biocatalytic one-step and multi-step reactions to biocatalytic total synthesis

In the area of human-made innovations to improve the quality of life, biocatalysis has already had a great impact and contributed enormously to a growing number of catalytic transformations aimed at the detection and analysis of compounds, the bioconversion of starting materials and the preparation of target compounds at any scale, from laboratory small scale to industrial large scale. The key enabling tools which have been developed in biocatalysis over the last decades also provide great opportunities for further development and numerous applications in various sectors of the global bioeconomy. Systems biocatalysis is a modular, bottom-up approach to designing the architecture of enzyme-catalyzed reaction steps in a synthetic route from starting materials to target molecules. The integration of biocatalysis and sustainable chemistry in vitro aims at ideal conversions with high molecular economy and their intensification. Retrosynthetic analysis in the chemical and biological domain has been a valuable tool for target-oriented synthesis while, on the other hand, diversity-oriented synthesis builds on forward-looking analysis. Bioinformatic tools for rapid identification of the required enzyme functions, efficient enzyme production systems, as well as generalized bioprocess design tools, are important for rapid prototyping of the biocatalytic reactions. The tools for enzyme engineering and the reaction engineering of each enzyme-catalyzed one-step reaction are also valuable for coupling reactions. The tools to overcome interaction issues with other components or enzymes are of great interest in designing multi-step reactions as well as in biocatalytic total synthesis.

Preparative-Scale Enzymatic Synthesis of rac-Glycerol-1-phosphate from Crude Glycerol Using Acid Phosphatases and Phosphate

Glycerol is a byproduct of biodiesel production and is generated in large amounts, which has resulted in an increased interest in its valorization. In addition to its use as an energy source directly, the chemical modification of glycerol may result in value-added derivatives. Herein, acid phosphatases employed in the synthetic mode were evaluated for the enzymatic phosphorylation of glycerol. Nonspecific acid phosphatases could tolerate glycerol concentrations up to 80 wt % and pyrophosphate concentrations up to 20 wt % and led to product titers up to 167 g L-1 in a kinetic approach. In the complementary thermodynamic approach, phytases were able to condense glycerol and inorganic monophosphate directly. This unexpected behavior enabled the simple and cost-effective production of rac-glycerol-1-phosphate from crude glycerol obtained from a biodiesel plant. A preparative-scale synthesis on a 100 mL-scale resulted in the production of 16.6 g of rac-glycerol-1-phosphate with a reasonable purity (≈75 %).

Evaluation of Natural and Synthetic Phosphate Donors for the Improved Enzymatic Synthesis of Phosphate Monoesters

Undesired product hydrolysis along with large amounts of waste in form of inorganic monophosphate by-product are the main obstacles associated with the use of pyrophosphate in the phosphatase-catalyzed synthesis of phosphate monoesters on large scale. In order to overcome both limitations, we screened a broad range of natural and synthetic organic phosphate donors with several enzymes on a broad variety of hydroxyl-compounds. Among them, acetyl phosphate delivered stable product levels and high phospho-transfer efficiency at the lower functional pH-limit, which translated into excellent productivity. The protocol is generally applicable to acid phosphatases and compatible with a range of diverse substrates. Preparative-scale transformations using acetyl phosphate synthesized from cheap starting materials yielded multiple grams of various sugar phosphates with up to 433 g L-1 h-1 space-time yield and 75% reduction of barium phosphate waste.

Exploiting Acid Phosphatases in the Synthesis of Phosphorylated Monoalcohols and Diols

A set of phosphatases was evaluated for their potential to catalyze the regio‐ and stereoselective phosphorylation of alcohols using a high‐energy inorganic phosphate donor, such as di‐, tri‐ and polyphosphate. Parameters such as type and amount of phosphate donor and pH of the reaction were investigated in order to minimize the thermodynamically favored hydrolysis of the phosphate donor and the formed phosphate ester. Diols were monophosphorylated with high selectivities. This biocatalytic phosphorylation method provides selectively activated and/or protected synthetic intermediates for further chemical and/or enzymatic transformations and is applicable to a large scale (6.86 g) in a flow setup with immobilized phosphatase.

Continuous-flow reactor-based enzymatic synthesis of phosphorylated compounds on a large scale

Acid phosphatase, an enzyme that is able to catalyze the transfer of a phosphate group from cheap pyrophosphate to alcoholic substrates, was covalently immobilized on polymethacrylate beads with an epoxy linker (Immobeads-150 or Sepabeads EC-EP). After immobilization 70% of the activity was retained and the immobilized enzyme was stable for many months. With the immobilized enzyme we were able to produce and prepare D-glucose-6-phosphate, N-acetyl-D-glucosamine-6-phosphate, allyl phosphate, dihydroxyacetone phosphate, glycerol-1-phosphate, and inosine-5'-monophosphate from the corresponding primary alcohol on gram scale using either a fed-batch reactor or a continuous-flow packed-bed reactor.

Enzymatic production of 5'-inosinic acid by a newly synthesised acid phosphatase/phosphotransferase

5'-Nucleotides including 5'-inosinic acid have characteristic taste and important application in various foods as flavour potentiators. The selective nucleoside acid phosphatase/phosphotransferase (AP/PTase) can catalyse the synthesis of 5'-nucleotides by transfer of phosphate groups. In this study, a 747-bp gene encoding AP/PTase from Escherichia blattae was synthesised. After expression, the recombinant AP/PTase was purified using nickel-NTA. The optimal temperature and pH of this enzyme were 30°C and 5.0, respectively. The activity was partially inhibited by metal ions such as Hg(2+), Ag(+) and Cu(2+), but not by chelating reagents such as EDTA. The values of K(m) and V(max) for inosine were 40 mM and 3.5 U/mg, respectively. Using this purified enzyme, 16.83 mM of 5'-IMP was synthesised from 37 mM of inosine and the molar yield reached 45.5%. Homology modelling and docking simulation were discussed.