Engineered dehydrogenase biocatalysts for non-natural amino acids: efficient isolation of the d-enantiomer from racemic mixtures

Francesca Paradisi, Philip A. Conway, Anita R. Maguire, Paul C. Engel
  • Organic & Biomolecular Chemistry, January 2008, Royal Society of Chemistry
  • DOI: 10.1039/b809147a

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.

Perspectives

Professor Paul C Engel (Author)
University College Dublin

This was a fruitful collaboration between biochemists (enzymologists) and organic chemists. The biochemists had the tools to create novel biocatalysts while the chemists had the clear view of what would be valuable for synthetic chemistry. This was initially a collaboration between two Irish unversities (UCD and UCC) with the lead author, Dr. Paradisi, as a chemist working in a biochemistry lab., providing a crucial link.

The following have contributed to this page: Professor Paul C Engel