Generation and Screening of DszB Mutants for Enhanced Catalytic Activity




Maes, Eugene Guy

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The presence of a metabolic pathway for dibenzothiophene desulfurization has been reported in various bacterial organisms.1,2,3 The role of this pathway is to oxidize and remove sulfur from the organosulfur compounds, such as dibenzothiophene (DBT). The activation of the dibenzothiophene desulfurization (Dsz) pathway is a result of the induction of the plasmid-encoded dsz operon (cluster of genes) in absence of sulfate and sulfur-containing amino acids.1,4 The Dsz pathway has been the focus of increased study due to its potential to purify crude oil. The Dsz pathway involves four steps using four enzymes (DszA, DszB, DszC and DszD). In the final and rate-limiting step, DszB catalyzes the hydrolysis of 2-(2-yydroxyphenyl) benzenesulfinate (HPBS) to form inorganic sulfur and 2-hydroxybiphenyl (HBP).2 As the rate-limiting enzyme in the pathway, DszB does not display the magnitude of enzymatic activity necessary for the efficient mass purification of crude oil. The goal of the research described is to develop a method to increase the activity of the DszB enzyme using directed evolution. A mutant dszB gene library was generated from R. erythropolis strain IGTS8. It was ligated into the pBAD TOPO vector and screened for activity. The screen indicated that there were four mutants with activity significantly above wild-type activity, seven mutants with activity similar to wild-type and 82 mutants with activity significantly below wild-type activity. One mutant with enhanced activity was selected for further characterization.



desulfurization, enzyme activation, fossil fuels, purification


Maes, E. G. (2003). Generation and screening of DszB mutants for enhanced catalytic activity (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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