Enhancing and Reversing the Stereoselectivity of<i>Escherichia coli</i>Transketolase<i>via</i>Single-Point Mutations
作者:Mark E. B. Smith、Edward G. Hibbert、Alexander B. Jones、Paul A. Dalby、Helen C. Hailes
DOI:10.1002/adsc.200800489
日期:2008.11.3
successfully applied to a 96-well format, and new active TK mutants were identified, which gave 1,3-dihydroxypentan-2-one in high stereoselectivities. Remarkably, active-site single-point mutants were identified that were able to both enhance and reverse the stereoselectivity of TK.
Biocatalytic synthesis is now well established amongst catalytic methodologies as an extremely useful approach for the industrial synthesis of high-value compounds, due to its many advantages such as high reaction specificity and selectivity. However, engineering a biocatalytic process can be complex and time-consuming. This paper presents a modular microfluidic reactor and in-line filtration system for the rapid and small-scale evaluation of biocatalytic reactions. The system combines a substrate with a biocatalyst in free solution, incubates the two components until full conversion to product has been achieved, before extracting the product. The system has been applied to the transketolase-catalysed reaction of hydroxypyruvate (HPA) and glycolaldehyde (GA) to L-erythrulose, demonstrating complete conversion of substrate to product, complete retention of the enzyme and an overall yield of approximately 65%. The complete conversion of HPA and propanal to (3S)-1,3-dihydroxypentan-2-one with a mutant transketolase further demonstrated the applicability of the microfluidic system for organic synthesis. (C) 2012 Elsevier B.V. All rights reserved.
A Multidisciplinary Approach Toward the Rapid and Preparative-Scale Biocatalytic Synthesis of Chiral Amino Alcohols: A Concise Transketolase-/ω-Transaminase-Mediated Synthesis of (2<i>S</i>,3<i>S</i>)-2-Aminopentane-1,3-diol
作者:Mark E. B. Smith、Bing H. Chen、Edward G. Hibbert、Ursula Kaulmann、Kirsty Smithies、James L. Galman、Frank Baganz、Paul A. Dalby、Helen C. Hailes、Gary J. Lye、John M. Ward、John M. Woodley、Martina Micheletti
DOI:10.1021/op900190y
日期:2010.1.15
Chiral amino alcohols represent an important class of value-added biochemicals and pharmaceutical intermediates. Chemical routes to such compounds are generally step intensive, requiring environmentally unfriendly catalysts and solvents. This work describes a multidisciplinary approach to the rapid establishment of biocatalytic routes to chiral aminodiols taking the original synthesis of (2S,3S)-2-aminopentane-1,3-diol as a specific example. An engineered variant of Escherichi coli transketolase (D469T) was used for the initial asymmetric ynthesis of (3S)-1,3-dihydroxypentan-2-one from the achiral substrates propanal and hydroxypyruvate. A bioinformatics led strategy was then used to identify and clone an omega-transaminase from Chromobacterium violaceum (DSM30191.) capable of converting the product of the transketolase-catalysed step to the required (2S,3S)-2-aminopentane-1,3-diol using isopropylamine as an inexpensive amine donor. Experiments; to characterize, optimize and model the kinetics of each reaction step were performed at the 1 mL scale using previously established automated microwell processing techniques. The microwell results, provided excellent predictions of the reaction kinetics when the. bioconversions were subsequently scaled up to preparative scales in batch stirred-tank reactors. The microwell methods thus provide process chemists and engineers with a valuable tool for the rapid and early evaluation of potential synthetic strategies. Overall, this work describes a concise and efficient biocatalytic route to chiral amino alcohols and illustrates an integrated multidisciplinary approach to bioconversion process design and scale-up.
Towards a Mechanistic Understanding of Factors Controlling the Stereoselectivity of Transketolase
作者:Anna Baierl、Axel Theorell、Ursula Mackfeld、Philipp Marquardt、Friederike Hoffmann、Stephanie Moers、Katharina Nöh、Patrick C. F. Buchholz、Jürgen Pleiss、Martina Pohl
DOI:10.1002/cctc.201800299
日期:2018.6.21
relevant amino acids of TKs from different species, a standard numbering scheme was developed. Using this concept, H26, H261, and F434 were identified as the key residues which mediate stereoselectivity, where two main factors influenced the arrangement of ThDP‐bound donor and acceptor prior to carboligation: the relative orientation of the substrate side chains and the orientation of the acceptor carbonyl