302-72-7Relevant articles and documents
Rational engineering ofAcinetobacter tandoiiglutamate dehydrogenase for asymmetric synthesis ofl-homoalanine through biocatalytic cascades
Diao, Shiqing,Jiang, Shuiqin,Liu, Yan,Sun, Yangyang,Wang, Hualei,Wang, Liuzhu,Wei, Dongzhi
, p. 4208 - 4215 (2021/06/30)
l-Homoalanine, a useful building block for the synthesis of several chiral drugs, is generally synthesized through biocascades using natural amino acids as cheap starting reactants. However, the addition of expensive external cofactors and the low efficiency of leucine dehydrogenases towards the intermediate 2-ketobutyric acid are two major challenges in industrial applications. Herein, a dual cofactor-dependent glutamate dehydrogenase fromAcinetobacter tandoii(AtGluDH) was identified to help make full use of the intracellular pool of cofactors when using whole-cell catalysis. Through reconstruction of the hydrophobic network between the enzyme and the terminal methyl group of the substrate 2-ketobutyric acid, the strict substrate specificity ofAtGluDH towards α-ketoglutarate was successfully changed, and the activity obtained by the most effective mutant (K76L/T180C) was 17.2 times higher than that of the wild-type protein. A three-enzyme co-expression system was successfully constructed in order to help release the mass transfer restriction. Using 1 Ml-threonine, which is close to the solubility limit, we obtained a 99.9% yield ofl-homoalanine in only 3.5 h without adding external coenzymes to the cascade, giving 99.9% ee and a 29.2 g L?1h?1space-time yield. Additionally, the activities of the engineeredAtGluDH towards some other hydrophobic amino acids were also improved to 1.1-11.2 fold. Therefore, the engineering design of some dual cofactor-dependent GluDHs could not only eliminate the low catalytic activity of unnatural substrates but also enhance the cofactor utilization efficiency of these enzymes in industrial applications.
Mechanistic insight into metal ion-catalyzed transamination
Mayer, Robert J.,Kaur, Harpreet,Rauscher, Sophia A.,Moran, Joseph
supporting information, p. 19099 - 19111 (2021/11/22)
Several classes of biological reactions that are mediated by an enzyme and a co-factor can occur, to a slower extent, not only without the enzyme but even without the co-factor, under catalysis by metal ions. This observation has led to the proposal that metabolic pathways progressively evolved from using inorganic catalysts to using organocatalysts of increasing complexity. Transamination, the biological process by which ammonia is transferred between amino acids and α-keto acids, has a mechanism that has been well studied under enzyme/co-factor catalysis and under co-factor catalysis, but the metal ion-catalyzed variant was generally studied mostly at high temperatures (70-100 °C), and the details of its mechanism remained unclear. Here, we investigate which metal ions catalyze transamination under conditions relevant to biology (pH 7, 20-50 °C) and study the mechanism in detail. Cu2+, Ni2+, Co2+, and V5+ were identified as the most active metal ions under these constraints. Kinetic, stereochemical, and computational studies illuminate the mechanism of the reaction. Cu2+ and Co2+ are found to predominantly speed up the reaction by stabilizing a key imine intermediate. V5+ is found to accelerate the reaction by increasing the acidity of the bound imine. Ni2+ is found to do both to a limited extent. These results show that direct metal ion-catalyzed amino group transfer is highly favored even in the absence of co-factors or protein catalysts under biologically compatible reaction conditions.
Biocatalysed synthesis of chiral amines: continuous colorimetric assays for mining amine-transaminases
Gourbeyre, Léa,Heuson, Egon,Charmantray, Franck,Hélaine, Virgil,Debard, Adrien,Petit, Jean-Louis,de Berardinis, Véronique,Gefflaut, Thierry
, p. 904 - 911 (2021/02/26)
In the course of our research aimed at the design of new biocatalytic processes for the enantioselective synthesis of chiral amines, we have developed new continuous assays for the screening of amine-transaminase collections. These assays are based on the use of hypotaurine as an irreversible amine donor. This β-aminosulfinic acid is converted upon transamination into 2-oxoethylsulfinic acid, which instantaneously decomposes into acetaldehyde and sulfite ions that can be easily detected by spectrophotometry using Ellman's reagent. Two complementary assays were developed based on this titration method. Firstly, a direct assay allowed detection of various transaminases able to use hypotaurine as an amino donor. In a second coupled assay,l-alanine is used as a generic donor substrate of amine-transaminases and is regenerated using an auxiliary hypotaurine-transaminase. The powerful and complementary nature of both assays was demonstrated through the screening of a collection of 549 amine-transaminases from biodiversity, thus allowing the discovery of a variety of valuable new biocatalysts for use in synthetic processes.