The amino acid gamma-carboxyglutamic acid (Gla) is found in four blood-clotting proteins, in a bone protein, in kidney protein, and in the protein present in various ectopic calcifications. This paper reports the presence of Gla in the EDTA-soluble, nondialyzable proteins of calcium-containing renal calculi including calcium oxalate, hydroxyapatite, and mixed stores of apatite and struvite (MgNH4PO4). Calculi composed of pure struvite and those composed of only uric acid or cystine do not contain Gla. From calcium oxalate and hydroxyapatite stontes, a protein of about 17,000 daltons was obtained which contained about 40 residues of Gla per 1,000 amino acids. The amino acid composition of this protein had no apparent relationship to the Gla-containing bone protein or to the similarly-sized F1 fragment of prothrombin which contains about 64 residues of Gla per 1,000 amino acid residues. The Gla-rich protein in calcium-containing renal stones thus may be a different Gla-containing protein. These data as well as other studies demonstrating the presence of Gla in pathologically calcified tissues not normally containing Gla suggest that the Gla-containing proteins may be of considerable pathophysiological significance.
J B Lian, E L Prien Jr, M J Glimcher, P M Gallop
The Editorial Board will only consider comments that are deemed relevant and of interest to readers. The Journal will not post data that have not been subjected to peer review; or a comment that is essentially a reiteration of another comment.