Conformational Change of 2-(2’ Hydroxyphenyl)Benzenesulfinate Desulfinase during Catalysis

Increasingly stringent regulation of sulfur oxide emissions and environmental stewardship necessitates more effective fossil fuel desulfurization technologies. While traditional catalytic means of desulfurization effectively remove simple sulfur compounds, more complex thiophenic molecules remain intact; these thiophenic molecules now account for the majority of sulfur emissions from liquid transportation fuels. Biodesulfurization via enzyme catalysis has the potential for highly specific, rapid thiophenic desulfurization occurring at ambient temperature and pressure. The 4-step catabolic pathway converts dibenzothiophene (DBT), a common crude oil contaminant, into the sulfur-free molecule 2-hydroxybiphenyl (2-HBP) without the disruption of carbon-carbon bonds. 2-hydroxybiphenyl desulfinase (DszB), the rate-limiting enzyme in this biocatalytic process, is capable of selectively cleaving carbon-sulfur bonds. Accordingly, fundamental understanding of the molecular mechanisms of DszB must be developed. Based on crystallographic evidence, we hypothesize that DszB undergoes an active site conformational change associated with the catalytic mechanism. Moreover, we anticipate this conformational change is responsible, in part, for enhancing product inhibition. Rhodococcus erythropolis IGTS8 DszB was recombinantly produced and purified via Escherichia coli BW25113 to test these hypotheses. Activity and the resulting conformational change of DszB in the presence of 2-HBP were tested. The activity of recombinant DszB appears comparable to the natively expressed enzyme and is inhibited via competitive binding of the product, 2-HBP. Using circular dichroism, we observed conformational changes in DszB upon introduction of product, 2-HBP.