Abstract:The inhibitory effect of sorghum episperm procyanidin tetramer(SEPT) on the initial adherence of Streptococcus sobrinus 6715 and its cariogenic factor glucosyltransferase (GTF) was investigated. The saliva-coated hydroxyapatite (SHA) was used as an in vitro model to measure the inhibitory effect of SEPT on the initial adherence of S. sobrinus 6715. The GTF-I catalytic region (CAT) gene of S. sobrinus 6715 was amplified by polymerase chain reaction (PCR), cloned into a Pgex-4T-1 vector, and transformed into T7 Express competent of Escherichia coli. The protein expression was induced by isopropyl β-D-1-thiogalactopyranoside (IPTG), and the expressed product was purified and concentrated to obtain the GTF-I/CAT target protein. Subsequently, different concentrations of SEPT samples were used to treat GTF-I/CAT, and the inhibitory effect of SEPT on GTF-I/CAT enzyme activity was determined based on the amount of water-insoluble glucan (WIG) formed by GTF-I/CAT. The results showed that SEPT could effectively decrease the initial adherence of S. sobrinus 6715 to SHA in a dose-dependent manner. The enzyme activity of GTF-I/CAT obtained from the gene cloning and expression was 8.446 mIU and the WIG formation ability was 1.603 mg/(mg?h). SEPT could effectively suppress the formation of WIG by acting on GTF-I/CAT (p<0.01). The results demonstrated that SEPT was effective in inhibiting the initial adherence of S. sobrinus 6715 to SHA and reducing WIG synthesis by acting on the CAT region of GTF-I. Therefore, SEPT can decrease the adhesion and aggregation of S. sobrinus 6715 on tooth surface and inhibit the sucrose-dependent adherence, thereby preventing the occurrence of dental caries.
