Biochemical characterization and structure prediction of the Cerrado soil CRB2(1) metagenomic dioxygenase

Dioxygenases are enzymes involved in the conversion of polyconic aromatic hydroxycarbons (PAHs), attracting significant biotechnological interest for the conversion of recalcitrant organic compounds. Furthermore, few studies show that dioxygenases can take on the function of resistance genes in clones. This enzymatic versatility opens up new opportunities for elucidating the mechanisms of microbial resistance, as well as its biotechnological application. In this work, a Cerrado soil dioxygenase named CRB2(1) was biochemically characterized. The enzyme was shown to have optimal activity at pH 7; a temperature of 30 °C; and using iron ions as a cofactor for substrate cleavage. The kinetic catalytic parameters of CRB2(1) were V_max = 0.02281 µM/min and K_M = 97.6. Its predicted three-dimensional structure obtained using the Modeller software v9.22 based on the crystal structure of gentisate 1,2-dioxygenase from Silicibacter pomeroyi (GDOsp) (PDB ID 3BU7, resolution 2.80 Å, residues 17-374) revealed substrate binding to the cupin domain, where the active site is located. The analyzed substrates interact directly with the iron ion, coordinated by three histidine residues. Changing the iron ion charge modifies the binding between the active site and the substrates. Currently, there is a demand for enzymes that have biotechnological activities of interest. Metagenomics allows analyzing the biotechnological potential of several organisms at the same time, based on sequence and functional activity analyses.