Fig.2
Metal ions can interact with amino acid residues and change the three-dimensional structure of enzymes,which could affect the substrate channel that substrates access or egress [20].
The software Caver 3.0.3 was used to simulate the substrate channel. As shown in Fig.S2, the peptide linker (green) and the loop region were at the end of the enzyme molecule. Adding the peptide linker changed the substrate channel (blue), which may affect the enzyme activity [21].