The reappraisal of nephrocalcin - its role in the inhibition of calcium oxalate crystal growth and interaction with divalent metal ions

Nephrocalcin (NC) is a potent crystal growth inhibitor of calcium oxalate m onohydrate. However, the sequence is undefined owing to its multiple glycos ylations. Although there have been many biochemical studies of the binding capacity of calcium, the study of the function of the domain is still defer red. By using S-200 gel filtration and Mono Q ion-exchange chromatographic procedures, NC can be purified without Further treatment for the removal of urobilirubin. The kinetic study of crystal growth in calcium oxalate monoh ydrate is performed using a seed slurry system. NC was cut into two peptide s through interaction with copper ion and ascorbic acid. The interaction si te of the copper ion is presumed to be located between 8 and 6 kDa of molec ular weight in NC. The data suggest that divalent metal ions may be involve d in the calcium oxalate crystallization through interaction with NC. The r ole of ascorbic acid in the formation of urinary stones should be reapprais ed for its association in the redox reaction, with resultant protein digest ion in the presence of copper ions.