Deepoxidase

Deepoxidase is an enzyme that catalyzes the oxidative cleavage of dithiolane rings in certain sulfur-containing compounds. It is found primarily in deep-sea bacterial species that participate in the sulfur cycle in hydrothermal vent environments. The enzyme is a metalloprotein that binds a mononuclear iron center which facilitates the generation of a highly reactive radical intermediate. The catalytic mechanism involves the abstraction of a hydrogen atom from a vicinal thiol group, leading to a ring-opening reaction that produces a sulfinic acid and a ketone fragment. Because of its high activation energy barrier, deepoxidase activity is only observed under extreme environmental conditions such as high pressure and low temperature.

Biochemists discovered deepoxidase in the genome of the obligate chemosynthetic bacterium Thiomicrospira profunda during a survey of hydrothermal vent microbiota in the Mariana Trench. Recombinant expression in E. coli and subsequent purification allowed kinetic analyses, revealing a Michaelis constant in the micromolar range and a turnover number of ~200 s‑1 at 4 °C. The enzyme’s apparent stability makes it a potential biocatalyst for the selective oxidation of sulfur-containing pharmaceutical intermediates. Further research into its crystal structure is underway, with the aim of engineering variants with improved activity at ambient conditions.