Abstract:［Objective］To reconstitute the in vitro catalytic activity of the individual dehydratase or cyclase domain of bifunctional bovicin HJ50 synthase BovM,and lay a foundation for the further investigation of catalytic mechanism of class II lantibiotic synthase LanM．［Method］The truncated proteins of BovM containing the N-terminal dehydratase domain or C-terminal cyclase domain were expressed in E．coli and purified． Substrate BovA,the precursor of bovicin HJ50,was incubated with these truncated BovM proteins in in vitro reaction system．The antimicrobial activity assay and MALDI-TOF MS analysis were used to monitor the dehydratase or cyclase activity of these truncated proteins． Meanwhile,the synergistic activities of both truncated proteins were tested in vivo and in vitro．［Results］The N-and C-terminal domains of BovM possessed dehydration and cyclization activity respectively．However,no synergistic activity was detected between these two functional domains．［Conclusion］The individual functional domains of BovM could execute their corresponding functions independently,but the intactness of BovM was important for its full modification activity.