The catalytic efficiency of MCOs and the range of substrates oxidized are determined partly by the redox potential of the type-1 copper that shuttles electrons from substrates to the trinuclear copper centre. Previous studies with CotA demonstrate the ability to manipulate the redox potential and catalytic efficiency of this enzyme through substituting amino acids involved in coordinating or stabilizing the type-I copper site (Durão et al., ,). In particular, replacing Met502 by leucine or phenylalanine increased the redox potential of CotA, while replacing L386 and I494 with alanine decreased the redox potential and catalytic efficiency of the enzyme.