Isolation and characterization of calcium oxalate crystal growth inhibitors from human urine

Four acidic polypeptides which inhibit the growth of calcium oxalate crystals have been isolated from normal human urine, and two of these have been characterized with respect to their amino acid and carbohydrate compositions. SDS-Polyacrylamide gel electrophoresis of either of the two latter inhibitors revealed one prominent band that migrated with an apparent molecular weight of 17,500 daltons. γ-Carboxyglutamate is present in these inhibitors, and they contain a total of more than 25% glutamic and aspartic acids and less than 10% of basic amino acids.