[Protein inhibitors of crystallization. Their characterization and potential role in calcium lithiasis]

Human saliva, pancreatic juice and urine are usually supersaturated with respect to calcium phosphate, calcium carbonate and calcium oxalate, respectively. The potential precipitation of these salts is prevented by unusual phosphoproteins which are normally present in these biological fluids. In vitro, such phosphoproteins are able to suppress the crystal growth of calcium salts; their physiological level is high enough to fulfill this function in vivo. The main molecular characteristics of these phosphoproteins are described and their biological function, as crystallization inhibitors, are discussed by the authors.