D-glyceric acid (DGA) is an intermediate of serine catabolism and of a minor pathway of fructose metabolism. The only known fate of DGA is phosphorylation to 3-phospho-D-glyceric acid (3PDGA) by cytosolic glycerate kinase (GLYCTK) (Yu et al. 2006). Defects in GLYCTK can cause D-glyceric aciduria (D-GA; MIM:220120), a rare inborn error of serine and fructose metabolism where DGA is excreted in large amounts in the urine. A variable phenotype is observed, ranging from severe mental retardation and death to milder speech delays and normal development (Van Schaftingen 1989, Sass et al. 2010).