It can be synthesized in the human body under normal physiological circumstances, making it a nonessential amino acid.

It is also the precursor to numerous other metabolites, including sphingolipids and folate, which is the principal donor of one-carbon fragments in biosynthesis.

[citation needed] D-Serine, synthesized in neurons by serine racemase from L-serine (its enantiomer), serves as a neuromodulator by coactivating NMDA receptors, making them able to open if they then also bind glutamate.

[19] Apart from central nervous system, D-serine plays a signaling role in peripheral tissues and organs such as cartilage,[20] kidney,[21] and corpus cavernosum.

To provide a basis for improving the understanding of the epidemiology, genotype/phenotype correlation and outcome of these diseases their impact on the quality of life of patients, as well as for evaluating diagnostic and therapeutic strategies a patient registry was established by the noncommercial International Working Group on Neurotransmitter Related Disorders (iNTD).

One example is spastic tetraplegia, thin corpus callosum, and progressive microcephaly, a disease caused by mutations that affect the function of the neutral amino acid transporter A.

The classification of L-serine as a non-essential amino acid has come to be considered as conditional, since vertebrates such as humans cannot always synthesize optimal quantities over entire lifespans.

A 2011 meta-analysis found adjunctive sarcosine to have a medium effect size for negative and total symptoms of schizophrenia.

[33] D-serine, which is made in the brain, has been shown to work as an antagonist/inverse co-agonist of t-NMDA receptors mitigating neuron loss in an animal model of temporal lobe epilepsy.