Molecular and enzymatic characterization of βC‐S lyase in Streptococcus constellatus

Background/aims: Streptococcus anginosus and Streptococcus constellatus are frequently isolated from dental abscesses and other suppurative lesions. We previously reported that βC-S lyase from a strain of S. anginosus produced significantly more hydrogen sulfide than βC-S lyases from other streptococci. The purpose of this study was to establish the molecular and enzymatic features of the βC-S lyase in S. constellatus and to elucidate whether this unique capacity is common to many strains of S. constellatus and S. anginosus. Methods:  The capacity of crude extract to produce hydrogen sulfide was evaluated among 16 strains of S. constellatus, S. anginosus, and Streptococcus gordonii. The lcd gene encoding βC-S lyase was cloned from the genomic DNA of each strain to compare the deduced amino acid sequences. The recombinant βC-S lyases of three representative strains were purified and characterized. Results:  Incubation of crude extracts from all strains of S. constellatus and S. anginosus with l-cysteine resulted in the production of a large amount of hydrogen sulfide. The primary sequence of βC-S lyase was very similar among strains of S. constellatus and S. anginosus. The kinetic properties of the βC-S lyases purified from S. constellatus resembled those for βC-S lyases purified from S. anginosus. In contrast, the βC-S lyases of S. constellatus and S. gordonii differed in terms of their hydrogen sulfide production, with the former producing much more. Conclusion:  A high level of hydrogen sulfide production, which appears to be a common feature in both S. constellatus and S. anginosus, may be associated with their abscess formation.