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Biochemical and clinical characteristics of creatine deficiency syndromes

100%

Sykut-Cegielska J., Gradowska W., Mercimek-Mahmutoglu S., Stockler-Ipsiroglu S.

Acta Biochimica Polonica

2004

tom 51

nr 4

Creatine deficiency syndromes are a newly described group of inborn errors of creatine synthesis (arginine:glycine amidinotransferase (AGAT) deficiency and guanidinoacetate methyltransferase (GAMT) deficiency) and of creatine transport (creatine transporter (CRTR) deficiency). The common clinical feature of creatine deficiency syndromes is mental retardation and epilepsy suggesting main involvement of cerebral gray matter. The typical biochemical abnormality of creatine deficiency syndromes is cerebral creatine deficiency, which is demonstrated by in vivo proton magnetic resonance spectroscopy. Measurement of guanidinoacetate in body fluids may discriminate between the GAMT (high concentration), AGAT (low concentration) and CRTR (normal concentration) deficiencies. Further biochemical characteristics include changes in creatine and creatinine concentrations in body fluids. GAMT and AGAT deficiency are treatable by oral creatine supplementation, while patients with CRTR deficiency do not respond to this type of treatment. The creatine deficiency syndromes are underdiagnosed, so their possibility should be considered in all children affected by unexplained mental retardation, seizures and speech delay.

Methylation demand: a key determinant of homocysteine metabolism

72%

Brosnan J. T., Jacobs R. L., Stead L. M., Brosnan M. E.

Acta Biochimica Polonica

2004

tom 51

nr 2

Elevated plasma homocysteine is a risk factor for cardiovascular disease and Alzheimer's disease. To understand the factors that determine the plasma homocysteine level it is necessary to appreciate the processes that produce homocysteine and those that remove it. Homocysteine is produced as a result of methylation reactions. Of the many methyltransferases, two are, normally, of the greatest quantitative importance. These are guanidinoacetate methyltransferase (that produces creatine) and phosphatidylethanolamine ^-methyltransferase (that produces phosphatidylcholine). In addition, methylation of DOPA in patients with Parkinson's disease leads to increased homocysteine production. Homocysteine is removed either by its irreversible conversion to cysteine (transsulfuration) or by remethylation to methionine. There are two separate remethylation reactions, catalyzed by betaine:homocysteine methyltransferase and methionine synthase, respectively. The reactions that remove homocysteine are very sensitive to B vitamin status as both the transsulfuration enzymes contain pyridoxal phosphate, while methionine synthase contains cobalamin and receives its methyl group from the folic acid one-carbon pool. There are also important genetic influences on homocysteine metabolism.

Ograniczanie wyników

2 Acta Biochimica Polonica

1 Brosnan J. T.

1 Brosnan M. E.

1 Gradowska W.

1 Jacobs R. L.

1 Mercimek-Mahmutoglu S.

1 Stead L. M.

1 Stockler-Ipsiroglu S.

1 Sykut-Cegielska J.

2 2004

Wyniki wyszukiwania

Biochemical and clinical characteristics of creatine deficiency syndromes

Methylation demand: a key determinant of homocysteine metabolism