Study on interaction between human salivary α-amylase and sorghum procyanidin tetramer: Binding characteristics and structural analysis.

As one of receptors of the acquired membrane, human salivary α‑amylase (HSA) plays an important role in the formation of caries. In vitro conditions, sorghum procyanidins (SPC) tetramer has a better inhibitory effect on the adhesion of Streptococcus mutans to hydroxyapatite than SPC-dimer and SPC-trimer. This study investigated the interaction mechanism between HSA and SPC-tetramer using spectroscopic techniques including fluorescence, UV-vis absorption, and circular dichroism (CD). Fluorescence data revealed that the fluorescence quenching of HSA by SPC-tetramer was a static quenching process, and that the SPC-tetramer was bound with HSA at the ratio of 1:1 in SPC-tetramer-protein complex. Meanwhile, the analysis of CD demonstrated that the conformation of HSA was altered in the presence of SPC-tetramer. The conformation changes of HSA might contribute to the reduction of the adhesion of cariogenic bacteria and finally decrease the occurrence of dental caries.