title: Lactate racemase. Hydroxylamine-dependent 18O exchange of the alpha-hydroxyl of lactic acid.
abstract: The lactic acid racemase (EC 5.1.2.1) derived from Clostridium butylicum catalyzes the racemization of the alpha-18O label. The proposed alpha-carbonyl intermediate for the enzyme-catalyzed reaction has been previously shown to be trapped as an enzyme-bound oxime in the presence of hydroxylamine. This report demonstrates that the formation of the inactive enzyme-bound oxime, followed by reactivation in the presence of an excess of competing free carbonyl (pyruvic acid) results in a complete loss of the alpha-18O label from an original alpha-18O-labeled lactic acid.
mesh_terms: D003013:Clostridium / Q000201:enzymology; D006880:Hydroxy Acids; D006898:Hydroxylamines; D007535:Isomerases / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism*; D010100:Oxygen; D010104:Oxygen Radioisotopes; D019998:Racemases and Epimerases / Q000378:metabolism*
chemical_list: D006880:Hydroxy Acids; D006898:Hydroxylamines; D007773:Lactates; D010104:Oxygen Radioisotopes; D007535:Isomerases; D019998:Racemases and Epimerases; D010100:Oxygen