One‐step Synthesis of α‐Keto Acids from Racemic Amino Acids by A Versatile Immobilized Multienzyme Cell‐free System

• Published in: ChemCatChem 2018-07, Vol.10 (14), p.3002-3011
• Main Authors: Orrego, Alejandro H., López‐Gallego, Fernando, Espaillat, Akbar, Cava, Felipe, Guisan, José M., Rocha‐Martin, Javier
• Format: Article
• Language: English
• Subjects: alpha-keto acids; Amino acid oxidase; Amino acids; Beads; biocatalysis; Catalase; Chemical synthesis; Cosmetics; dynamic kinetic resolution; Enantiomers; Enzymes; Glutaraldehyde; Hydrogen peroxide; immobilization; PLP-dependent enzymes; Thermal stability; α-keto acids
• ISSN: 1867-3880; 1867-3899; 1867-3899
• DOI: 10.1002/cctc.201800359

The elevated value of α‐keto acids has pushed scientists to explore more efficient and less expensive alternatives for their synthesis. In this work, an immobilized tri‐enzyme system that produced α‐keto acids in “one‐pot” from l‐ or racemic mixtures of diverse amino acids was presented. The system combined a broad‐spectrum amino acid racemase (BsrV), a d‐amino acid oxidase (DAAO) and catalase (CAT). BsrV racemized l‐amino acids into their d‐enantiomers, DAAO catalyzed the stereospecific oxidative deamination of the d‐amino acids into their corresponding α‐keto acids, ammonium ion, and H2O2. Finally, CAT converted the inactivating H2O2 into H2O and O2, which can be reused by the oxidase reaction. BsrV thermal stability was improved 3,300‐fold by immobilizing the enzyme on glyoxyl‐activated agarose beads. DAAO and CAT were co‐immobilized on agarose beads functionalized with glutaraldehyde groups for enhancing their stabilities and eliminating H2O2 in a much more effective way. To show the versatility of this system, racemic mixtures of amino acids were converted in their corresponding α‐keto acids. The coupling of the three immobilized enzymes permitted conversions of approximately 99 % through a dynamic kinetic resolution process. This system conserved 100 % of its initial effectiveness after 8 reaction cycles. Collectively, our innovative tri‐enzyme system for the synthesis of α‐keto acids opens the door for a cheapening in the production of many pharmaceutical and cosmetics. All for one: A heterogenized multienzyme one‐pot system combining a broad‐spectrum amino acid racemase (BsrV), a D‐amino acid oxidase (DAAO) and catalase (CAT) can produce α‐keto acids with conversions of approximately 99 % through a dynamic kinetic resolution process.