gamma-L-glutamyltaurine.
The discovery of the dipeptide gamma-glutamyltaurine (gamma-GT; glutaurine, Litoralon) in the parathyroid in 1980 and later in the brain of mammals gave rise to studies on intrinsic and synthetic taurine peptides of this type. It was suggested that gamma-glutamyltransferase (GGT; gamma-glutamyltranspeptidase) in the brain is responsible for the in vivo formation of this unusual dipeptide. gamma-GT has been prepared by both synthetic and enzymatic methods. The chemical syntheses included the use of protecting groups and coupling methods. A wide spectrum of analytical and spectroscopic methods was used to confirm the structure of the synthetic compounds and to elucidate the position of the peptide bond. Enzymatic preparation of gamma-GT from taurine takes advantage of the selective transpeptidation action of GGT on L-glutamine, glutathione, gamma-glutamyl-p-nitroanilide or other glutamine donors. Although the functional roles of gamma-GT in the brain are only poorly understood, many of its established CNS effects have been reported in the last 25 years. Its effect on emotional arousal and its anti-conflict potencies are synergistic with the anxiolytic drug diazepam. gamma-GT exhibits anti-conflict potency, which is exerted by reducing aversion or phobia and/or the anxiety levels. gamma-GT also acts as endogenous modulator in excitatory aminoacidergic neurotransmission. It is suggested that such acidic peptides through N-methyl-D-aspartic acid receptors could be part of the neurochemical substrate underlying self-stimulation of the medial prefrontal cortex. Other gamma-GT effects in neural systems include: effects on the monoamine concentration in the brain; effects on aggressive behavior in the cat; effects on thyroid hormones in the rat; amelioration of electroshock-induced amnesia; potent and long-lasting antiepileptic action (on intra-amygdaloid injection); affect the glutamatergic system in schizophrenic disorders. Roles for gamma-GT in non-neural systems have also been reported, e.g., effects on the metamorphosis of amphibians; on plasma rennin regulation; on radiation protection; on uric acid levels; on human antibody-dependent cell-mediated cytotoxicity (ADCC) and many more.
Bittner
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S
Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel. bittner@bgumail.bgu.ac.il
Win
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T
Gupta
R
R
D000663:Amphibians / Q000502:physiology; D000818:Animals; D002525:Cerebellar Cortex / Q000502:physiology; D004644:Emotions / Q000502:physiology; D005973:Glutamine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007107:Immune System / Q000502:physiology; D008675:Metamorphosis, Biological / Q000502:physiology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013654:Taurine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013687:Telencephalon / Q000502:physiology; D013961:Thyroid Gland / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D005973:Glutamine; D013654:Taurine; C020903:glutaurine