concentrated enzyme extracts with higher specific activities. By performing the assay in the presence of various concentrations of ornithine, we confirmed that AGAT is inhibited by ornithine, as reported previously (7 ). This observation may be of clinical interest in conditions of hyperornithinemia. Decreased brain creatine has been observed in patients affected with gyrate atrophy of the chor...

Creatine is a nitrogen containing compound that serves as an energy shuttle between the mitochondrial sites of ATP production and the cytosol where ATP is utilized. There are two known disorders of creatine synthesis (both transmitted as autosomal recessive traits: arginine: glycine amidinotransferase (AGAT) deficiency; OMIM 602360; and guanidinoacetate methyltransferase (GAMT) deficiency (OMIM...

Cerebral creatine deficiency syndromes (CCDSs) are a group of inborn errors of creatine metabolism comprising two autosomal recessive disorders that affect the biosynthesis of creatine--i.e. arginine:glycine amidinotransferase deficiency (AGAT; MIM 602360) and guanidinoacetate methyltransferase deficiency (GAMT; MIM 601240)--and an X-linked defect that affects the creatine transporter, SLC6A8 d...

Background: Creatine transporter (CRTR) deficiency is the most common creatine deficiency syndrome, of which the final diagnosis relies on mutation in the X-linked CRTR gene. To date, more than 90 mutations in the SLC6A8 gene have been reported. This paper discusses a novel mutation detected via the thorough sequencing of all the X-chromosome-specific exons investigated in a four and a half yea...

Among cerebral creatine deficiency syndromes, guanidinoacetate methyltransferase (GAMT) deficiency can present the most severe symptoms, and is characterized by neurocognitive dysfunction due to creatine deficiency and accumulation of guanidinoacetate in the brain. So far, every patient was found with negligible GAMT activity. However, GAMT deficiency is thought under-diagnosed, in particular d...

The first inborn error of creatine metabolism (guanidinoacetate methyltransferase [GAMT] deficiency) has recently been recognized in an infant with progressive extrapyramidal movement disorder. The diagnosis was established by creatine deficiency in the brain as detected by in vivo magnetic resonance spectroscopy and by defective GAMT activity and two mutant GAMT alleles in a liver biopsy. Here...