Abstract: Objective This study aimed to produce bioactive autoinducer-2(AI-2) in vitro via molecular biological techniques, as well as provide a basis for further study on the cariogenic virulence regulation mechanism of AI-2 in Streptococcus mutans. Methods Effective prokaryotic recombinant systems for the expression and purification of S-ribosylhomocysteinase(LuxS) and S-adenosylhomocysteine nucleosidase(Pfs) proteins were constructed. After induction by isopropyl β-D-1-thiogalactopyranoside, expressing products were purified with the Ni-NTA spin column. AI-2, which is an informational molecule in quorum sensing, was produced in vitro using purified LuxS and Pfs. The bioactivity of AI-2 was tested by Vibrio harveyi BB170 luminescence bioassay, which indirectly proved the bioactivities of purified LuxS and Pfs. Results AI-2 produced in vitro could significantly induce the luminescence of Vibrio harveyi. Furthermore, its luminous intensity was much higher than that induced by the AI-2 produced naturally by a bacterial colony of Streptococcus mutans UA159. Conclusion An efficient expression system for soluble recombinant proteins of LuxS and Pfs was established. The highly active AI-2 was manufactured, which could provide essential materials for further research.

Key words: Streptococcus mutans, quorum sensing, autoinducer-2, S-ribosyl homocysteinase