D-amino acids from racemic mixtures: quantitative enzymatic removal of L-enantiomer
What is it about?
D-amino acids are valuable, high-cost synthetic building blocks. Our paper describes an efficient way of making them by quantitatively removing the L-form from a 50:50 racemic mixture of L- and D- forms. We used an L-amino acid dehydrogenase, in which the active site had been mutated to extend substrate specificity, in order to remove the L-amino acid by oxidation with NAD+. To drive the reaction to completion we used a second enzyme, alcohol dehydrogenase, and 5% ethanol to continuously recycle NADH. The method was ssuccessfully tested by making several substituted phenylalanine derivatives on a millimole scale.
Why is it important?
A barrier to use of enzymes for green chemistry in the past has been the limited specificity range of biological catalysts. Knowledge of enzyme structure, coupled with gene technology has made it possible to redesign enzymes to accept more nad different substrates. This is the key to the success of our method, offering a simple route to D-amino acids from the racemic compounds, thus avoiding the need for chiral synthesis.
The following have contributed to this page: Professor Paul C Engel
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