A novel enzyme, 2 '-hydroxybiphenyl-2-sulfinate desulfinase (DszB), from a dibenzothiophene-desulfurizing bacterium Rhodococcus erythropolis KA2-5-1: gene overexpression and enzyme characterization

作者：Nakayama N; Matsubara T; Ohshiro T; Moroto Y; Kawata Y; Koizumi K; Hirakawa Y; Suzuki M; Maruhashi K; Izumi Y^*; Kurane R

来源：Biochimica et Biophysica Acta-Proteins and Proteomics, 2002, 1598(1-2): 122-130.

DOI：10.1016/S0167-4838(02)00365-5

• dibenzothiophene
• desulfurization
• desulfinase
• purification
• molecular chaperon

Dibenzothiophene (DBT), a model of organic sulfur compound in petroleum, is microbially desulfurized to 2-hydroxybiphenyl (2-HBP), and the gene operon dszABC was required for DBT desulfurization. The final step in the microbial DBT desulfurization is the conversion of 2'-hydroxybiphenyl-2-sulfinate (HBPSi) to 2-HBP catalyzed by DszB. In this study, DszB of a DBT-desulfurizing bacterium Rhodococcus erythropolis KA2-5-1 was overproduced in Escherichia coli by coexpression with chaperonin genes, groEL/groES, at 25 degreesC. The recombinant DszB was purified to homogeneity and characterized. The optimal temperature and pH for DszB activity were 35 degreesC and about 7.5, respectively. The K-m and k(cat) values for HBPSi were 8.2 muM and 0.123.s(-1), respectively. DszB has only one cysteine residue, and the mutant enzyme completely lost the activity when the cysteine residue was changed to a serine residue. This result together with experiments using inhibitors showed that the cysteine residue contributes to the enzyme activity. DszB was also inhibited by a reaction product, 2-HBP (K-i = 0.25 mM), and its derivatives, but not by the other reaction product, sulfite. The enzyme showed it narrow substrate specificity: only 2-phenylbenzene sulfinate except HBPSi served as a substrate among the aromatic and aliphatic sulfinates or sulfonates tested. DszB was thought to be a novel enzyme (HBPSi desulfinase) in that it could specifically cleave the carbon-sulfur bond of HBPSi to give 2-HBP and sulfite ion without the aid of any other proteinic components and coenzymes.

• 出版日期2002-7-29