D-Serine

NMDA receptors are critical for brain functions such as learning, memory, and the formation of new synapses. D-serine is the “mirror image” (enantiomer) of the more common amino acid L-serine and is produced in the body from L-serine by the enzyme serine racemase. D-serine is an amino acid that functions as a signaling molecule in the brain, where it helps activate N-methyl-D-aspartate (NMDA) receptors.