A Novel Cold-Adapted Catechol 1,2-Dioxygenase From Antarctic Sea-Ice Bacterium Halomonas sp. ANT108: Characterization and Immobilization.

The enzyme catechol 1,2-dioxygenase (CAT) plays a critical role in the biosynthesis pathway of cis, cis-muconic acid (CCMA), which serves as an indispensable raw material for various industrial applications. In this research, we cloned a novel cold-adapted CAT (HaCAT) from the Antarctic sea ice bacterium Halomonas sp. ANT108. Homology modeling analysis revealed that HaCAT possessed the characteristic Fe³⁺ binding site and catalytic active site of typical CATs, and it exhibited unique structural adaptations to cold environments. The optimal temperature and pH for recombinant HaCAT (rHaCAT) were found to be 25°C and 6.5, respectively. At 0°C, the enzyme retained a maximum activity of 43.6%, and in the presence of 1.0 M NaCl, its activity reached 173.9%, demonstrating significant salt tolerance. Additionally, the V_max and K_m of rHaCAT were 6.68 μmol/min/mg and 128.90 μM at 25°C, respectively. Furthermore, rHaCAT was successfully immobilized in the metal-organic framework ZIF-8 and retained almost 50% of its activity after five reuse cycles, demonstrating excellent reusability. Overall, these results provided a new resource and theoretical foundation for the industrial biocatalytic production and modification of CAT.