Enzymatic Preparation of an (S)-Amino Acid from a Racemic Amino Acid

Shortening Synthetic Routes to Small Molecule Active Pharmaceutical Ingredients Employing Biocatalytic Methods

Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.

Biocatalytic Reduction Reactions from a Chemist's Perspective

Reductions play a key role in organic synthesis, producing chiral products with new functionalities. Enzymes can catalyse such reactions with exquisite stereo-, regio- and chemoselectivity, leading the way to alternative shorter classical synthetic routes towards not only high-added-value compounds but also bulk chemicals. In this review we describe the synthetic state-of-the-art and potential of enzymes that catalyse reductions, ranging from carbonyl, enone and aromatic reductions to reductive aminations.

Development of a Combination Fermentation Strategy to Simultaneously Increase Biomass and Enzyme Activity of D-amino Acid Oxidase Expressed in Escherichia coli

D-amino acid oxidase (DAAO) is widely used in the industrial preparation of L-amino acids, and cultivating Escherichia coli (E. coli) expressing DAAO for the biosynthesis of L-phosphinothricin (L-PPT) is very attractive. At present, the biomass production of DAAO by fermentation is still limited in large-scale industrial applications because the expression of DAAO during the fermentation process inhibits the growth of host cells, which limits higher cell density. In this study, the factors that inhibit the growth of bacterial cells during a 5-L fed-batch fermentation process were explored, and the fermentation process was optimized by co-expressing catalase (CAT), by balancing the biomass and the enzyme activity, and by adding exogenous D-alanine (D-Ala) to relieve the limitation of DAAO on the cells and optimize fermentation. Under optimal conditions, the DO-STAT feeding mode with DO controlled at 30% ± 5% and the addition of 27.5 g/L lactose mixed with 2 g/L D-Ala during induction at 28 °C resulted in the production of 26.03 g dry cell weight (DCW)/L biomass and 390.0 U/g DCW specific activity of DAAO; an increase of 78% and 84%, respectively, compared with the initial fermentation conditions. The fermentation strategy was successfully scale-up to a 5000-L fermenter.

Simultaneous synthesis of l-DOPA and oxidation of d-amino acid by specific coupling of a peroxidase to d-amino acid oxidase

3,4 Dihydroxy phenyl l-alanine (L-DOPA) is the gold standard Parkinson's disease therapy. A heme-dependent peroxidase (HDP) catalyzes the ortho-hydroxylation of l-tyrosine to l-DOPA using H₂O₂ as the co-substrate. d-amino acid oxidase (DAAO) catalyzes the oxidative deamination of d-amino acids (e.g. d-alanine), and H₂O₂ is evolved. However, both the enzymes DAAO and HDP can be inactivated by H₂O₂ during the catalysis. In situ generation and utilization of H₂O₂ can siginificatly reduce the inactivation by H₂O₂. HDP exists as a monomer and DAAO is a dimeric enzyme. Herein, the C-terminus of HDP was specifically ligated to the N-terminus of the DAAO subunit with native peptide through the in vivo monomer-subunit splicing. In the splicing product HDP&DAAO, HDP is close to the DAAO subunit at a molecular distance, and the transfer of H₂O₂ from DAAO to HDP is facilitated. In addition, HDP&DAAO exhibited a higher stability than HDP. Kinetics analysis showed that both the substrates l-tyrosine and d-alanine obey the Michaelis-Menten kinetics. For the deamination of d-alanine, the catalytic efficiency of HDP&DAAO is 3.05 times that of DAAO. For the sybthesis of l-DOPA from l-tyrosine, the catalytic efficiency of HDP&DAAO is 1.58 times that of HDP. Furthermore, HDP&DAAO was encapsulated within a Znic-based coordination polymer (Zn-CP). The morphorogy of HDP&DAAO/Zn-CP can be regulated by the enzyme concentration, the catalytic efficiency of the conjugates was found to be dependent on the morphorogy. The conjugates HDP&DAAO/Zn-CP exhibited a higher catalytic efficiency than free HDP&DAAO.

Application of ω-Transaminases in the Pharmaceutical Industry

Chiral amines are valuable building blocks for the pharmaceutical industry. ω-TAms have emerged as an exciting option for their synthesis, offering a potential "green alternative" to overcome the drawbacks associated with conventional chemical methods. In this review, we explore the application of ω-TAms for pharmaceutical production. We discuss the diverse array of reactions available involving ω-TAms and process considerations of their use in both kinetic resolution and asymmetric synthesis. With the aid of specific drug intermediates and APIs, we chart the development of ω-TAms using protein engineering and their contribution to elegant one-pot cascades with other enzymes, including carbonyl reductases (CREDs), hydrolases and monoamine oxidases (MAOs), providing a comprehensive overview of their uses, beginning with initial applications through to the present day.

Biocatalysis for synthesis of pharmaceuticals

Chirality is a key factor in the safety and efficacy of many drug products and thus the production of single enantiomers of drug intermediates and drugs has become important and state of the art in the pharmaceutical industry. There has been an increasing awareness of the enormous potential of microorganisms and enzymes (biocatalysts) for the transformation of synthetic chemicals with high chemo-, regio- and enatioselectivities providing products in high yields and purity. In this article, biocatalytic processes are described for the synthesis of key chiral intermediates for development pharmaceuticals.

Concise Redox Deracemization of Secondary and Tertiary Amines with a Tetrahydroisoquinoline Core via a Nonenzymatic Process

A concise deracemization of racemic secondary and tertiary amines with a tetrahydroisoquinoline core has been successfully realized by orchestrating a redox process consisted of N-bromosuccinimide oxidation and iridum-catalyzed asymmetric hydrogenation. This compatible redox combination enables one-pot, single-operation deracemization to generate chiral 1-substituted 1,2,3,4-tetrahydroisoquinolines with up to 98% ee in 93% yield, offering a simple and scalable synthetic technique for chiral amines directly from racemic starting materials.

Enhancement of the solubility and stability of D-amino acid oxidase by fusion to an elastin like polypeptide

An elastin-like polypeptide (ELP) was fused to D-amino acid oxidases (DAAO). ELP-DAAO exhibited a better solubility in aqueous solutions than DAAO, and its enzymatic activity is about 1.6 times that of DAAO. The stability of the proteins was investigated by interacting with urea at various concentrations. The circular dichroism and fluorescence spectra were measured. The results demonstrated that that ELP-DAAO exhibited a much better stability than DAAO, and ELP-DAAO has retained the α-helix content with a high percentage even at a high urea concentration. The results of this work have demonstrated that the ELP tag can be utilized to purify DAAO, in the meantime the solubility and stability of the enzyme are improved.

Biocatalytic synthesis of chiral alcohols and amino acids for development of pharmaceuticals

Chirality is a key factor in the safety and efficacy of many drug products and thus the production of single enantiomers of drug intermediates and drugs has become increasingly important in the pharmaceutical industry. There has been an increasing awareness of the enormous potential of microorganisms and enzymes derived there from for the transformation of synthetic chemicals with high chemo-, regio- and enatioselectivities. In this article, biocatalytic processes are described for the synthesis of chiral alcohols and unntural aminoacids for pharmaceuticals.