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.