D-Glyceric Acidemia: Biochemical Studies of a New Syndrome

Abstract

Extract: Studies of a mentally retarded boy, clinically suffering from nonketotic hyperglycinemia, are reported. Using combined gas chromatography-mass spectrometry, enzyme specificity studies, and spectropolariometry D-glyceric acid in extremely elevated concentrations was demonstrated in both serum and urine (serum: 1.0–1.3 mmol/liter, urine: 33–187 mmol/liter). Hydroxypyruvic acid was not detectable in urine from this boy using a gas chromatographic method with a limit of detection of 0.3 mmol/liter. Enzyme assays of D-glyceric dehydrogenase on blood leukocytes demonstrated significantly lower activity in the patient compared with five normal children. Speculation: The accumulation of glycine in this new metabolic defect may result from a secondary inhibition of the glycine cleavage system, an explanation that would correspond well with the current concept on the genesis of the glycine accumulation found in ketotic hyperglycinemia.