<unk>  is the simplest amino acid, having no stereoisomers. It can act as a neurotransmitter in the brain, act as an inhibitor in the spinal cord and brain stem, while having excitatory effects in the cortex of the brain.<unk>  is metabolized to final end products of ammonia and carbon dioxide through the<unk>  cleavage system (GCS), an enzyme complex made up of four protein subunits. Defects in these subunits can cause<unk> , although some causes of the disease are still unknown. Normally, GCS shows its highest enzymatic activity in liver, brain and placental tissue. One of its main functions is to maintain normal<unk>  levels in the brain. Defects in GCS cause an increase of<unk>  concentration in blood plasma and cerebrospinal fluid. The exact pathophysiology of the disorder is not known, but it is considered likely that buildup of<unk>  in the brain is responsible for the symptoms. All forms of<unk>  show elevated levels of<unk>  in the plasma, as well as in cerebral spinal fluid (CSF).<unk>  concentrations in the CSF of affected patients are typically more markedly elevated than in plasma, leading to a corresponding elevation in the ratio of<unk>  concentrations in the cerebral spinal fluid to that in the plasma. This ratio can also be slightly elevated in patients receiving valproic acid.<unk>  (nonketotic hyperglycinemia, or NKH) should not be confused with other metabolic disorders that can produce elevated<unk>  levels. For example, certain inherited 'organic acidurias' (aka 'organic acidemias') can produce elevated<unk>  in plasma and urine, although these disorders are not caused by defects in the<unk>  cleavage system, and they are not typically accompanied by corresponding elevations of<unk>  in cerebrospinal fluid (CSF).<unk>  is unique in the fact that levels of<unk>  are disproportionately elevated in CSF (in addition to elevations in blood and urine), whereas CSF<unk>  levels are normal or near-normal in patients with inherited organic acidurias.<unk>  metabolism<unk>  is metabolized in the body's cells to end products of carbon dioxide and ammonia. The<unk>  cleavage system, which is responsible for<unk>  metabolism in the mitochondria is made up of four protein subunits, the P-protein, H-protein, T-protein and L-protein.
Glycine encephalopathy
Toxic encephalopathy
Ethylmalonic encephalopathy
Wernicke encephalopathy
Post-encephalitic parkinsonism
Early myoclonic encephalopathy
Carbamate poisoning
Viral encephalitis