Catechol 2,3-dioxygenase from a new phenolic compound degrader Thauera sp. K11: purification and biochemical...

Catechol 2,3-dioxygenase (C23O) from a new phenolic compound degrader Thauera sp. K11 was purified and characterized. The native form of the enzyme was determined as a homotetramer with a molecular weight of 140 kDa, and its isoelectric point was close to 6.4. One iron per enzyme subunit was detected using atom absorption spectroscopy, and the effective size of C23O in its dilute solution (0.2 g L^-1 , pH 8.0) was 14.5 nm. The optimal pH and temperature were 8.4 and 45 °C, respectively. The addition of Mg²⁺ , Cu²⁺ , Fe²⁺ , and Mn²⁺ could improve the enzyme activity, while Ag⁺ was found to be a strong inhibitor. C23O was stable in alkali conditions (pH 7.6-11.0) and thermostable below 50 °C. The final purified C23O had a sheet content of 53%, consistent with the theoretical value. This showed that the purified catechol 2,3-dioxygenase folded with a reasonable secondary structure.