In addition to the known disease biomarkers, several other metabolites listed in Table 1 were expected to change: pyruvate, alanine, and glycine are directly involved in the AGT reaction; hydroxypyruvate is oxidized to glycerate by glyoxalate reductase/hydroxypyruvate reductase (GRHPR), the enzyme deficient in primary hyperoxaluria type 2 (PH2) that catalyzes the reduction of glyoxylate to glycolate (Cramer et al., 1999); serine also was expected to change because of the serine-pyruvate transaminase activity of AGT (Danpure, 2006). Here, GRHPR is linked to primary hyperoxaluria type 2.