Enzyme Engineering for High-Yielding Amide Formation: Lipase-Catalyzed Synthesis of N-Acyl Glycines in Aqueous Media

Engineering of methionine sulfoxide reductase A with simultaneously improved stability and activity for kinetic resolution of chiral sulfoxides

Methionine sulfoxide reductase A (MsrA) has emerged as promising biocatalysts in the enantioselective kinetic resolution of racemic (rac) sulfoxides. In this study, we engineered robust MsrA variants through directed evolution, demonstrating substantial improvements of thermostability. Mechanism analysis reveals that the enhanced thermostability results from the strengthening of intracellular interactions and increase in molecular compactness. Moreover, these variants demonstrated concurrent improvements in catalytic activities, and notably, these enhancements in stability and activity collectively contributed to a significant improvement in enzyme substrate tolerance. We achieved kinetic resolution on a series of rac-sulfoxides with high enantioselectivity under initial substrate concentrations reaching up to 93.0 g/L, representing a great improvement in the aspect of the substrate concentration for biocatalytic preparation of chiral sulfoxide. Hence, the simultaneously improved thermostability, activity and substrate tolerance of MsrA represent an excellent biocatalyst for the green synthesis of optically pure sulfoxides.

Enzymatic Strategies for the Biosynthesis of N-Acyl Amino Acid Amides

Amide bond-containing biomolecules are functionally significant and useful compounds with diverse applications. For example, N-acyl amino acids (NAAAs) are an important class of lipoamino acid amides with extensive use in food, cosmetic and pharmaceutical industries. Their conventional chemical synthesis involves the use of toxic chlorinating agents for carboxylic acid activation. Enzyme-catalyzed biotransformation for the green synthesis of these amides is therefore highly desirable. Here, we review a range of enzymes suitable for the synthesis of NAAA amides and their strategies adopted in carboxylic acid activation. Generally, ATP-dependent enzymes for NAAA biosynthesis are acyl-adenylating enzymes that couple the hydrolysis of phosphoanhydride bond in ATP with the formation of an acyl-adenylate intermediate. In contrast, ATP-independent enzymes involve hydrolases such as lipases or aminoacylases, which rely on the transient activation of the carboxylic acid. This occurs either through an acyl-enzyme intermediate or by favorable interactions with surrounding residues to anchor the acyl donor in a suitable orientation for the incoming amine nucleophile. Recently, the development of an alternative pathway involving ester-amide interconversion has unraveled another possible strategy for amide formation through esterification-aminolysis cascade reactions, potentially expanding the substrate scope for enzymes to catalyze the synthesis of a diverse range of NAAA amides.

Immobilization of Lipases Using Poly(vinyl) Alcohol

Lipases are very versatile enzymes because they catalyze various hydrolysis and synthesis reactions in a chemo-, regio-, and stereoselective manner. From a practical point of view, immobilization allows the recovery and stabilization of the biocatalyst for its application in different types of bioreactors. Among the various support options for immobilizing lipases is polyvinyl alcohol (PVA), which, when functionalized or combined with other materials, provides different characteristics and properties to the biocatalyst. This review analyzes the multiple possibilities that PVA offers as a material to immobilize lipases when combined with alginate, chitosan, and hydroxypropylmethylcellulose (HPMC), incorporating magnetic properties together with the formation of fibers and microspheres. The articles analyzed in this review were selected using the Scopus database in a range of years from 1999 to 2023, finding a total of 42 articles. The need to expand knowledge in this area is due to the great versatility and scaling possibilities that PVA has as a support for lipase immobilization and its application in different bioreactor configurations.