The role of the one-carbon cycle in neuropsychiatric disease.

This paper reviews and correlates three separate recent findings that implicate the one-carbon cycle in neuropsychiatric disease: (i) the demonstration by kinetic studies that the Vmax of methionine adenosine transferase (MAT) is reduced in some schizophrenics and depressives and is increased in some manics, and that the activity of serine hydroxymethyltransferase (SHMT) is reduced in a further subpopulation of schizophrenics; (ii) the demonstration that S-adenosylmethionine (the product of MAT) is an effective clinical antidepressant; and (iii) the reports that L-methionine is an effective treatment for certain of the symptoms of Parkinson's disease. These clinical findings may be correlated with recent findings that transmethylation reactions (lipid and carboxymethylation) play an important role in synaptic events (coupling of receptors to adenylate cyclase and release of neurotransmitters).