(sat-1), a gene responsible for oxalate transportation, allowing it to increase sat-1 mRNA expression and as a result oxalate efflux from the cell. The increased oxalate release allows the buildup of calcium oxalate in the urine, and thus the eventual formation of kidney stones. The disruption of glyoxylate metabolism provides an additional mechanism of hyperoxaluria development. Loss of function mutations in the HOGA1 gene leads to a loss of the 4-hydroxy-2-oxoglutarate aldolase, an enzyme in the hydroxyproline to glyoxylate pathway. The glyoxylate resulting from this pathway is normally stored away to prevent oxidation to oxalate in the cytosol. The disrupted pathway, however, causes a buildup of 4-hydroxy-2-oxoglutarate which can also be transported to the cytosol and converted into glyoxylate through a different aldolase. These glyoxylate molecules can be oxidized into oxalate increasing its concentration and causing hyperoxaluria. Reactions and uses Glyoxylic acid is about ten times stronger an acid than acetic acid, with an acid dissociation constant of 4.7 × 10−4 (pK''a = 3.32): OCHCO2H + H+ With base, glyoxylic acid disproportionates, forming hydroxyacetic acid and oxalic acid: 2 OCHCO2H + H2O → HOCH2CO2H + HO2CCO2H Glyoxylic acid gives heterocycles upon condensation with urea and 1,2-diaminobenzene. Phenol derivatives In general, glyoxylic acid undergoes an electrophilic aromatic substitution reaction with phenols, a versatile step in the synthesis of several other compounds. The immediate product with phenol itself is 4-hydroxymandelic acid. This species reacts with ammonia to give hydroxyphenylglycine, a precursor to the drug amoxicillin. Reduction of the 4-hydroxymandelic acid gives 4-hydroxyphenylacetic acid, a precursor to the drug atenolol. The sequence of reactions, in which glyoxylic acid reacts with guaiacol the phenolic component followed by oxidation and decarboxylation, provides a route to vanillin as a net formylation process. Hopkins Cole reaction Glyoxylic acid is a component of the Hopkins–Cole reaction, used to check for the presence of tryptophan in proteins. Environmental chemistry Glyoxylic acid is one of several ketone- and aldehyde-containing carboxylic acids that together are abundant in secondary organic aerosols. In the presence of water and sunlight, glyoxylic acid can undergo photochemical oxidation. Several different reaction pathways can ensue, leading to various other carboxylic acid and aldehyde products. Safety The compound is not very toxic with an for rats of 2500 mg/kg. References Conjugated aldehydes Aldehydic acids