D-amino acid dehydrogenase
| D-arginine dehydrogenase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 1.4.99.6 | ||||||||
| CAS no. | 37205-44-0 | ||||||||
| Alt. names | D-amino-acid dehydrogenase | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
D-amino-acid dehydrogenase (EC 1.4.99.1, transferred to 1.4.99.6) is a bacterial enzyme that catalyses the oxidation of D-amino acids into their corresponding oxoacids. It contains both flavin and nonheme iron as cofactors. The enzyme has a very broad specificity and can act on most D-amino acids.
D-amino acid + H2O + acceptor <=> a 2-oxo acid + NH3 + reduced acceptor
This reaction is distinct from the oxidation reaction catalysed by D-amino acid oxidase that uses oxygen as a second substrate, as the dehydrogenase can use many different compounds as electron acceptors, with the physiological substrate being coenzyme Q.
D-amino acid dehydrogenase is an enzyme that catalyzes NADPH from NADP+ and D- glucose to produce D- amino acids and glucose dehydrogenase. Some but not limited to these amino acids are D-leucine, D-isoleucine, and D-Valine, which are essential amino acids that humans cannot synthesize because they are not included in their diet. Moreover, D- amino acids catalyzes the formation of 2-oxo acids to produce D- amino acids in the presence of DCIP which is an electron acceptor. D-amino acids are used as components of pharmaceutical products, such as antibiotics, anticoagulants, and pesticides, because they have been shown to be not only more potent than their L enantiomers, but also more resistant to enzyme degradation. D-amino acid dehydrogenase enzymes have been synthesized via mutagenesis with an ability to produce straight, branched, cyclic aliphatic and aromatic D-amino acids. Solubilized D-amino acid dehydrogenase tends to increase its affinity for D-alanine, D-asparagine, and D--amino-n-butyrate.
In E. coli K12 D-amino acid dehydrogenase is most active with D-alanine as its substrate, as this amino acid is the sole source of carbon, nitrogen, and energy. The enzyme works optimally at pH 8.9 and has a Michaelis constant for D-alanine equal to 30 mM. DAD discovered in gram-negative E. coli B membrane can convert L-amino acids into D-amino acids as well.
Additionally, D- amino acid dehydrogenase is used in Dye-Linked dehydrogenase (Dye-DHs) which uses artificial dyes such as 2,6-Dichloroindophenol (DCIP) as their electron acceptor rather than using their natural electron acceptors. This can accelerate the reaction between the enzyme and the substrate when the electrons are being transferred.