STUDIES ON THE PURIFICATION AND PROPERTIES OF d-GLYCERIC ACID KINASE OF LIVER

Previous studies on the biosynthesis of serine (1, 2) revealed that n-glyceric acid served as a precursor for this amino acid in the presence of ATP.1 This suggested the occurrence of a kinase that catalyzes the formation of PGA from glyceric acid.This paper reports the results of studies on the purification and properties of the glyceric acid kinase from horse liver.EXPERIMENTAL Materials-nn-Glyceric acid-3-C14 was prepared by the Isotopes Specialties Company, Inc., Burbank, California.Samples of pure n-glyceric acid and nn-glyceric acid were kindly furnished by Dr. C. E. Ballou of the Department of Biochemistry of this University.ATP and PGA were purchased from the Nutritional Biochemicals Corporation and ADP from the Sigma Chemical Company.Analytical MethodsGlyceric acid was determined by oxidation with periodate and calorimetric determination of the formaldehyde formed by employing the same conditions as those used for serine estimation in the method of Frisell et al. (3).Protein in the enzyme incubations was determined with the combined copper sulfate-phenol reagent of Sutherland et al. ( 4)) inorganic phosphate by the method of Lowry and Lopez (5)) and organic phosphate by the method of Fiske and Subbarow (6).Chromatographic procedures employed are described in connection with the experiments to which they are pertinent.Enzyme Assay-The activity of glyceric acid kinase was assayed by the rate of disappearance of glyceric acid.The incubation was carried out for 30 minutes at 37" in 12 ml.conical centrifuge tubes containing 3 pmoles of