Glutamate (neurotransmitter)
Glutamate is a major constituent of a wide variety of proteins; consequently it is one of the most abundant amino acids in the human body. Under ordinary conditions enough is obtained from the diet that there is no need for any to be synthesized. Nevertheless, glutamate is formally classified as a non-essential amino acid, because it can be synthesized from alpha-Ketoglutaric acid, which is produced as part of the citric acid cycle by a series of reactions whose starting point is citrate. Glutamate cannot cross the blood-brain barrier unassisted, but it is actively transported into the nervous system by a high affinity transport system, which maintains its concentration in brain fluids at a fairly constant level.
D-amino acid oxidase activator
D-amino acid oxidase activator (DAOA, also known as G72) is a protein enriched in various parts of brain, spinal cord, and testis. DAOA is thought to interact with D-amino acid oxidase, a peroxisomal enzyme, and its gene was associated with schizophrenia in a number of studies. In separate studies it has been shown to confer susceptibility to bipolar disorder. Therefore, it has been important in researching whether the Kraepelinian dichotomy is genuine. The gene itself was discovered during an investigation of chromosomal 13q22-q34 region, which was previously linked to schizophrenia. G72 is transcribed into several proteins due to alternative splicing; the longest protein is called LG72 and consists of 153 amino acids. Although the protein was initially found to interact with DAO in yeast 2-hybrid experiment, one recent in vivo experiment showed LG72 presence only in mitochondria and failed to confirm the interaction.