Evolving a stereochemically promiscuous aldolase to create new classes of stereoselective biocatalyst for asymmetric synthesis

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This proposal describes the use of a thermostable enzyme to prepare new types of chiral compounds as building blocks for synthesising important intermediates for the pharmaceutical and fine chemical industry. The scope and limiation of the enzyme to catalyse a specific reaction with a wide range of substrates will be investigated. The enzyme contains an active site where catalysis takes place, and its structure has been characterised at a molecular level by X-ray crystallography. Knowledge of the structure of this active site will enable us to generate new 'mutant' catalysts with their own specificity profiles as improved biocatalysts for synthesis. These mutation studies will fall into two categories: firstly, we will deliberately introduce specific changes into the enzyme; and secondly, we will generate random mutations to afford large libraries of catalysts. Screening protocols will be developed that will enable us to rapidly identify mutants with useful catalytic activity, with the aim of identifying biocatalysts that carry out reactions not currently observed in nature. Concurrently, we will also develop a chemical approach to the synthesis of these type of compounds, using small chiral molecules as alternative catalysts. A number of compounds produced in this study will then be converted into novel highly fuctionalised intermediates of use for the synthesis of biologically-important natural products.