Metalloantibodies: mercury(II)-dependent acyl transferases

A new approach for the elicitation of metal-dependent catalytic antibodies for ester hydrolysis is described. A coordinatively unsaturated mercury complex 1-(Hg) , has been utilized as a hapten to elicit antibodies that incorporate mercury(II) as a Lewis acid cofactor. From a panel of monoclonal antibodies generated to 1-(Hg) , antibody 38G2 was found to hydrolyze the ester 3 in the presence of HgCl 2 [ K m app( 3 )=345 μM; K m app(Hg 2+ )=87 μM; k cat app/ k uncat =3×10 2 ]. This is the first example of a biocatalyst that enlists mercuric ion as a cofactor and it is anticipated that this approach will open new avenues for exploitation of metals thought previously beyond the scope of protein catalysts.