References

Alves PM, Nunes R, Zhang C, Maycock CD, Sonnewald U, et al. 2000. Metabolism of3-13C-malate in primary cultures of mouse astrocytes. Dev Neurosci 22 456-462. Aoki C, Milner TA, Berger SB, Sheu KF, Blass JP, et al. 1987. Glial glutamate dehydrogenase Ultrastructural localization and regional distribution in relation to the mito-chondrial enzyme, cytochrome oxidase. J Neurosci Res 18 305-318. Bak LK, Sickmann HM, Schousboe A, Waagepetersen HS. 2005. Activity of the lactate-alanine shuttle is...

Serine Glycine and Threonine

Klomp 2 Metabolism of l-Serine, Glycine, and Threonine 25 2.1 l-Serine Biosynthesis 2.2 l-Serine Utilization 2.2.1 Glycine and One-Carbon Group Production by l-Serine 2.2.2 l-Serine and Phospholipid 2.2.3 l-Serine and Synthesis of Glycine and 2.3 Glycine Biosynthesis 2.4 Glycine Utilization 2.5 l-Threonine Utilization 3 l-Serine in the Central Nervous System 29 3.1 l-Serine During Central Nervous System Development 3.2 Functions of l-Serine-Derived...

LThreonine Utilization

In contrast to l-serine and glycine, l-threonine is an indispensable or essential amino acid and uptake from the diet is therefore required. There are no data to support the existence of l-threonine synthesis routes of any significance in humans. In mammals, at least two enzymes are involved in l-threonine utilization, namely l-threonine 3-dehydrogenase (EC 1.1.1.103) and l-threonine dehydratase (EC 4.3.1.19) (0 Figure 2-2). Metabolic pathways of L-threonine. Enzymes involved I, L-threonine...

Mechanism and Consequences of Histidinemia

Histidinemia is a result of histidase deficiency (Ghadimi, 1961). It appears to be inherited as an autosomal recessive disorder that affects the liver (Selden et al., 1995). Recently, mutations in the histidase gene were identified (Kawai et al., 2005). Four missense mutations (R322P, P259L, R206T, and R208L), two exonic polymorphisms (T141T c.423A Tand P259P c.777A G), and two intronic polymorphisms (IVS6-5T C and IVS9 + 25A G) have been identified (Kawai et al., 2005). It is frequently but...

Brain Disorders Related to Histidinemia

Early reports on clinical symptoms associated with histidinemia or consequences of histidinemia included a number of neurological and psychiatric abnormalities. However, the majority of the patients seem to be asymptomatic (Tada et al., 1982, 1984 Sano et al., 1997). In one prospective study on 16 families, the IQ scores, visiomotor integration, and skills in reading and mathematics were analyzed in probands and siblings (mean age 9.5 years) with histidinemia (none treated with a low-histidine...

GABAGlutamate Glutamine Cycle

A flow of glutamate occurs from the neuronal to the astrocytic compartment during glutamatergic neurotransmission O Figure 1-1 . This flow needs to be compensated for by a flow of a glutamate precursor in the opposite direction owing to the lack of a neuronal anaplerotic pathway. Although it has recently been shown that carboxylation of pyruvate, presumably via mitochondrial malic enzyme, can occur in cultured cerebellar granule cells Hassel and Brathe, 2000 , the extent to which this occurs at...

Histidine

1 Introduction 2 Histidine Transport and Uptake in 3 Metabolism of Histidine 4 Histidine as Histamine Precursor 5 Histidinemia 5.1 Mechanism and Consequences of Histidinemia 5.2 Brain Disorders Related to 5.3 Portocaval Anastomosis and Histidinemia 6 Summary and Abstract Histidine is metabolized through three different pathways, of which decarboxylation to histamine yields the active neurotransmitter histamine in the tuberomamillary neurons of the brain. l-Histidine is transported into the...

LThreonine in the Central Nervous System

It is obvious that l-threonine, being an essential amino acid, is necessary for protein synthesis in the CNS. Recent data show that the CNS senses changes in essential amino acid concentrations very rapidly, in particular in response to dietary sources deficient of essential amino acids such as l-threonine, and this must have played an important role in human evolution Hao et al., 2005 . In contrast, there is surprisingly little data available on specific functions of l-threonine in the CNS. In...

Clinical Relevance of Glycine 431 Hyperekplexia

Hyperekplexia or hereditary startle disease is a predominantly autosomal dominant disorder caused by a defective function of the GR. In rare cases, the disorder is caused by autosomal recessive defects of GLRA1, the p-subunit of the GR, mutations in the GR-clustering proteins gephyrin and collybistin, or by defects in the glycine transporter GlyT2 Rees et al., 2006 . The main features of the disorder are disturbances of muscle tone and an exaggerated startle response usually to auditory...

Serine Transport

Uptake and transport of l-serine occurs through several transport systems, including the Na -dependent neutral amino acid transporter ASCT, system A amino acid transporters, and the Na -independent transporter system L asc transporters. The neutral amino acid transporters ASCT1 and ASCT2 transport l-alanine, l-serine, l-cysteine, and l-threonine, whereas ASCT2 in addition also transports l-glutamine, l-asparagine, l-methionine, l-leucine, and glycine albeit with different affinities for the...