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

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Abstract

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.

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