Fig. 5

The mechanism of improved enzyme activity of CatA^N211S revealed by homologous modeling and molecular docking. (a) relative activity to 4-cholocatechol of CatA and CatA^N211S; (b) homodimer structure of CatA calculated by Swiss-Model, Fe(III) is shown as orange ball; (c) spatial distance of 4-cholocatechol and Fe(III) in the CatA activity pocket; (d) spatial distance of 4-cholocatechol and Fe (III) in CatA^N211S activity pocket; (e) proposed catalytic mechanism of CatA: I, catechol firstly coordinates with Fe(III) to form a semialdehyde structure; II, oxygen carries out a nucleophilic attack on the unilateral hydroxyl group in an electron transfer process; III, a Criegee 1,2-rearrangement (involving the simultaneous cleavage of the O1-O2 and C3-C4 bonds concerted with formation of a bond between O2 and O3) and a proton transfer process happens; IV leads to muconic acid