Binding characteristics of Streptococcus mutans for calcium and casein phosphopeptide

Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP) and may be used to localize ACP in dental plaque, maintaining a state of supersaturation with respect to tooth enamel, reducing demineralization and enhancing remineralization [Reynolds, J Dent Res 1997;76:1587-1595]. The aim of this paper is to investigate these effects by measuring the affinity and capacity of Streptococcus mutans for CPP-ACP. Using the equilibrium dialysis system described by Rose and Hogg [Biochim Biophys Acta 1995;1245:94-98], assessment of calcium binding by a plaque streptococcus at a fixed CPP-ACP concentration gives a series of CPP-ACP-influenced dissociation constants for calcium. These data can then be used to derive a true dissociation constant for CPP-ACP itself. The results demonstrate that CPP-ACP binds with about twice the affinity of the bacterial cells for calcium up to a value of 0. 16 g/g wet weight cells. Application of CPP-ACP to plaque may cause a transient rise in plaque fluid free calcium which may assist remineralization. Subsequently, CPP-ACP will form a source of readily available calcium to inhibit demineralization. Hence, CPP-ACP binds well to plaque, providing a large calcium reservoir, which is likely to restrict mineral loss during a cariogenic episode and provide a potential source of calcium for subsequent remineralization. Overall, once in place, CPP-ACP will restrict the caries process.