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

Biochim Biophys Acta. 2002 Jul 29;1598(1-2):122-30. doi: 10.1016/s0167-4838(02)00365-5.

Abstract

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 degrees C. The recombinant DszB was purified to homogeneity and characterized. The optimal temperature and pH for DszB activity were 35 degrees C and about 7.5, respectively. The K(m) and k(cat) values for HBPSi were 8.2 microM 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 a 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cloning, Molecular
  • DNA Primers
  • Kinetics
  • Oxidoreductases / genetics
  • Oxidoreductases / isolation & purification
  • Oxidoreductases / metabolism*
  • Oxidoreductases Acting on Sulfur Group Donors
  • Polymerase Chain Reaction
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Rhodococcus / enzymology*

Substances

  • DNA Primers
  • Recombinant Proteins
  • Oxidoreductases
  • 2-(2-hydroxybiphenyl)-benzenesulfinate desulfinase
  • Oxidoreductases Acting on Sulfur Group Donors