An enzyme multimer is provided which comprises a plurality of monomer units including a first monomer unit having enzymatic activity and a second monomer unit having enzymatic activity, wherein each of the first monomer unit and the second monomer unit comprise a cysteine residue and the cysteine residues of each monomer unit are covalently bound to each other through a disulfide bond to covalently attach the first monomer unit to the second monomer unit.