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D-Amino Acid Dehydrogenase

Use in synthesis reactions

D-Amino Acid Dehydrogenase has shown itself to be effective in the synthesis of branched-chain amino acids such as D-Leucine, D-Isoleucine, and D-Valine. In the given study, researchers were successfully able to use D-amino acid dehydrogenase to create high amounts of these products from the starting material of 2-oxo acids, in the presence of ammonia. The conditions for this were variable, though the best results appeared at around 65°C.

Amino Acids obtained through these reactions resulted in a high enantioselectivity of >99% and high yields of >99%.

Given the nature of this enzyme, it may be possible to use it in order to create non-branched D-amino acids as well as modified D-amino acids.

Obtaining D-Amino Acid Dehydrogenase

In one study, in order to test the viability of using D-amino dehydrogenase in synthesis reactions, researchers used mutant bacteria to obtain and create different strains of the enzyme. These researchers found that it only required five mutations in order to modify the selective D-Amino Dehydrogenase into working with other D-amino acids. They also found that it retained its highly selective nature, capable of receiving mostly D-enantiomers after mutation, with yields in excess of 95%.

A heat-stable variant of D-amino acid dehydrogenase was found in the bacterium Rhodothermus marinus JCM9785. This variant is involved in the catabolism of trans-4-hydroxy-L-proline.

From the given studies, in order to obtain D-amino acid dehydrogenase one must first introduce and express it within a given bacterial species, some of which have been previously referenced. It must then be purified under favorable conditions. These are based upon the particular species of D-amino acid dehydrogenase used in a given research experiment. Under incorrect conditions, the protein may denature. For example, it was found that specifically D-alanine dehydrogenases from E. coli and P. aeruginosa would lose most of their activity when subjected to conditions of 37 - 42°C. After this, it is possible to separate and purify through existing methods.

Artificial D-Amino Acid Dehydrogenase

Due to the drawbacks of current methods, researchers have begun work on creating an artificial enzyme capable of producing the same D-amino acids as enzymes from naturally occuring sources. By adding five amino acids to a given sample isolated from U. thermosphaericus, they succeeded. By modifying the amino acid sequence, researchers were able to change the specificity of the molecule towards certain reactants and products, showing that it may be possible to use artificial D-amino acid dehydrogenase to screen for certain D-amino acid products.