Table 1.
Occurrence of d-amino acids in different organisms and their physiological importance
| Amino acid | Organism | Function | Reference |
|---|---|---|---|
| d-Ala, d-Ser, d-Asp, d-Asn, d-Glu, d-Gln | Bacteria | Cell wall (component of peptidoglycan) | 129 |
| d-Leu, d-Met, d-Phe, d-Tyr | Bacteria | Regulate the formation of peptidoglycan | 130 |
| d-Leu, d-Val, d-Phe | Bacteria | Part of gramicidin and gramicidin S | 131–134 |
| d-Met, d-Leu | Staphylococcus aureus | Biofilm inhibition | 15 |
| d-His | S. aureus | Staphylopine (metallophore: metal-scavenging peptide) | 135 |
| d-Ala, d-Ser, d-Asp | Archaea | Membrane-bound and free form | 24 |
| d-Ala | Phyllomedusa sauvagei (frog) | Dermorphin (part of heptapeptide that binds to opioid receptors) | 136, 137 |
| d-Met | P. sauvagei (frog) | Deltropin (part of heptapeptide that binds to opioid receptors) | 136, 137 |
| d-Trp | Conus radiatus (fish-hunting snail) | Contryphan (part of octapeptide; one of the constituents of venom) | 138 |
| d-Cys | Photuris lucicrescens (firefly) | Part of d-luciferin (natural substrate of luciferase) | 139, 140 |
| d-2,3-diamino-propionic acid, d-Ser | Bombyx mori (insect) | Involved in metamorphosis | 139 |
| d-Ala | Aquatic crustaceans and bivalve mollusks | Involved in maintaining cellular osmolarity | 141 |
| d-Asp | Mammals (nervous system/endocrine system/reproductive system) | Modulates NMDA receptor, Regulates secretion of hormones like vasopressin, oxytocin, prolactin, and testosterone | 26, 33 |
| d-Ser | Mammals (brain) | Co-agonist of NMDA receptor | 29, 30 |
| d-Ser | Arabidopsis thaliana | Crucial for pollen tube development | 36 |