A neonate with ornithine aminotransferase deficiency; insights on the hyperammonemia-associated biochemical phenotype of gyrate atrophy.

Unlabelled: Gyrate atrophy of the choroid and retina (GACR) secondary to deficiency of ornithine aminotransferase (OAT) is a rare autosomal recessive metabolic disorder usually diagnosed in childhood when patients develop myopia and a characteristic retinal degeneration accompanied by hyperornithinemia. Plasma ammonia is normal or sub-normal after the neonatal period. A few GACR patients present in early infancy with hyperammonemia, encephalopathy and a biochemical profile of low plasma ornithine, citrulline and arginine, with increased urinary excretion of homocitrulline and orotic acid, resembling a primary urea cycle disorder.

Phosphatase-inert glucosamine 6-phosphate mimics serve as actuators of the glmS riboswitch.

The glmS riboswitch is unique among gene-regulating riboswitches and catalytic RNAs. This is because its own metabolite, glucosamine-6-phosphate (GlcN6P), binds to the riboswitch and catalytically participates in the RNA self-cleavage reaction, thereby providing a novel negative feedback mechanism. Given that a number of pathogens harbor the glmS riboswitch, artificial actuators of this potential RNA target are of great interest.