Homocysteic acid

Homocysteic acid is a sulfur-containing amino acid that is a metabolite of the essential amino acid methionine. It is a potent excitatory neurotransmitter in the mammalian central nervous system and is implicated in a variety of neurological and psychiatric disorders.

Structure and Properties

Homocysteic acid is a dibasic acid with two carboxyl groups and one amino group. It has a molecular weight of 191.18 g/mol and a pKa of 2.1 and 9.8. It is soluble in water and insoluble in organic solvents.

Biosynthesis

Homocysteic acid is formed from homocysteine through the action of the enzyme cystathionine beta-synthase. This reaction also produces cystathionine, which is further metabolized to cysteine and alpha-ketobutyrate.

Function

Homocysteic acid acts as an excitatory neurotransmitter in the central nervous system by activating NMDA receptors and metabotropic glutamate receptors. It is also involved in the regulation of neuronal excitability and synaptic plasticity.

Clinical Significance

Elevated levels of homocysteic acid have been associated with several neurological and psychiatric disorders, including Alzheimer's disease, schizophrenia, and depression. It is also a potential biomarker for vitamin B12 deficiency and homocystinuria, a rare inherited disorder of methionine metabolism.

See Also

• Homocysteine
• Methionine
• Cystathionine beta-synthase
• NMDA receptor
• Metabotropic glutamate receptor

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