Covalently immobilize crude d-amino acid transaminase onto UiO-66-NH2 surface for d-Ala biosynthesis

Enzyme reaction has been accepted widely in numerous applications owing to the high efficiency and stereo-selectivity, as well as simple preparation by gene engineering. However, the fragility and complex purification process of the enzyme are long-standing problems which limit the large-scale application. One possible solution may be the enzyme immobilization. As one type of porous material with high loading capacity and designable functionality, Metal-Organic Frameworks (MOFs) are ideal choices for the immobilization of enzyme with a considerable interest in recent years. In this study, d-amino acid transaminase (DAT), an important enzyme for industrial synthesis of d-Ala, was covalently immobilized on the surface of a star MOFs material, UiO-66-NH_2. Interestingly, we found that the nanoscale hybrid enzyme UiO-66-NH₂-Gd-DAT not only maintained the high catalytic efficiency but also got rid of the interference of polluting enzymes, which meant that we could obtain efficient and stereo-selective immobilized enzyme without complex purification process. In general, our findings demonstrated that using UiO-66-NH₂ might be a promising strategy to immobilize enzyme and produce effective biocatalyst with high activity and stereo-selectivity.

Bio-Catalysis in Multicomponent Reactions

Enzyme catalysis is a very active research area in organic chemistry, because biocatalysts are compatible with and can be adjusted to many reaction conditions, as well as substrates. Their integration in multicomponent reactions (MCRs) allows for simple protocols to be implemented in the diversity-oriented synthesis of complex molecules in chemo-, regio-, stereoselective or even specific modes without the need for the protection/deprotection of functional groups. The application of bio-catalysis in MCRs is therefore a welcome and logical development and is emerging as a unique tool in drug development and discovery, as well as in combinatorial chemistry and related areas of research.

Overview on Multienzymatic Cascades for the Production of Non-canonical α-Amino Acids

The 22 genetically encoded amino acids (AAs) present in proteins (the 20 standard AAs together with selenocysteine and pyrrolysine), are commonly referred as proteinogenic AAs in the literature due to their appearance in ribosome-synthetized polypeptides. Beyond the borders of this key set of compounds, the rest of AAs are generally named imprecisely as non-proteinogenic AAs, even when they can also appear in polypeptide chains as a result of post-transductional machinery. Besides their importance as metabolites in life, many of D-α- and L-α-"non-canonical" amino acids (NcAAs) are of interest in the biotechnological and biomedical fields. They have found numerous applications in the discovery of new medicines and antibiotics, drug synthesis, cosmetic, and nutritional compounds, or in the improvement of protein and peptide pharmaceuticals. In addition to the numerous studies dealing with the asymmetric synthesis of NcAAs, many different enzymatic pathways have been reported in the literature allowing for the biosynthesis of NcAAs. Due to the huge heterogeneity of this group of molecules, this review is devoted to provide an overview on different established multienzymatic cascades for the production of non-canonical D-α- and L-α-AAs, supplying neophyte and experienced professionals in this field with different illustrative examples in the literature. Whereas the discovery of new or newly designed enzymes is of great interest, dusting off previous enzymatic methodologies by a "back and to the future" strategy might accelerate the implementation of new or improved multienzymatic cascades.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as burlemarxione A from Clusia burle-marxii.