Harada, A.

Org. Biomol. Chem. 2006, 4, 3571, 10.1039/B609242J

Monoclonal antibodies have been elicited against an achiral rhodium complex and this complex was used in the presence of a resultant antibody, 1G8, for the catalytic hydrogenation of 2-acetamidoacrylic acid to produce N-acetyl-L-alanine in high (>98%) enantiomeric excess.

Harada, A.; Yamaguchi, H.

Sci. Rep. 2019, 9, 10.1038/s41598-019-49844-0

Design and engineering of protein scaffolds are crucial to create artificial metalloenzymes. Herein we report the first example of C-C bond formation catalyzed by artificial metalloenzymes, which consist of monoclonal antibodies (mAbs) and C2 symmetric metal catalysts. Prepared as a tailored protein scaffold for a binaphthyl derivative (BN), mAbs bind metal catalysts bearing a 1,1?-bi-isoquinoline (BIQ) ligand to yield artificial metalloenzymes. These artificial metalloenzymes catalyze the Friedel-Crafts alkylation reaction. In the presence of mAb R44E1, the reaction proceeds with 88% ee. The reaction catalyzed by Cu-catalyst incorporated into the binding site of mAb R44E1 is found to show excellent enantioselectivity with 99% ee. The protein environment also enables the use of BIQ-based catalysts as asymmetric catalysts for the first time.

Harada, A.

Chem. Lett. 2008, 37, 1184-1189, 10.1246/cl.2008.1184

Monoclonal antibodies have been prepared against water-soluble porphyrins, viologen derivatives, and transition-metal complexes, respectively. These monoclonal antibodies were utilized to devise biosensing and catalytic systems.

Harada, A.

Chem. - Eur. J. 2004, 10, 6179-6186, 10.1002/chem.200305692

Peroxidase activity of a complex of water‐soluble cationic metalloporphyrin with anti‐cationic porphyrin antibody is reported. Antibody 12E11G, which was prepared by immunization with a conjugate of 5‐(4‐carboxyphenyl)‐10,15,20‐tris(4‐methylpyridyl)porphine iodide (3MPy1C), bound to tetramethylpyridylporphyrin iron complex (FeIII–TMPyP) with the dissociation constant of 2.6×10−7 M. The complex of antibody 12E11G with FeIII–TMPyP catalyzed oxidation of pyrogallol, catechol, and guaiacol. A Lineweaver–Burk plot for the oxidation of pyrogallol catalyzed by the FeIII–TMPyP–antibody complex showed Km=8.6 mM and kcat=680 min−1. Under the same conditions, Km and kcat for horseradish peroxidase (HRP) were 0.8 mM and 1750 min−1, respectively. Although the binding interaction of the antibody to the substrates was one order lower than that of native HRP, the peroxidase activity of this system was in the same order of magnitude as that of HRP.

Harada, A.

Inorg. Chem. 1997, 36, 6099-6102, 10.1021/ic9610849

Antibody 03-1, which was prepared by immunization with meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) conjugate, has been found to bind strongly to Mn(III)−TCPP and Fe(III)−TCPP complexes with dissociation constants of 4.1 × 10-7 and 1.5 × 10-7 M, respectively, although other monoclonal antibodies raised against TCPP did not bind to these TCPP−metal complexes. The complexes of antibody 03-1 with Mn(III)−TCPP and Fe(III)−TCPP were found to catalyze oxidation of pyrogallol selectively. A Lineweaver-Burk plot for the oxidation of pyrogallol by the antibody−Fe−TCPP complex showed Km = 4.0 mM and kcat = 50 min-1. Studies on the effect of the molar ratio of the antibody to metalloporphyrin on the catalytic activity showed that a 1:1 complex was the most effective for the reaction. The effect of salt (NaCl) on the reaction showed that electrostatic interaction between the antibody and the metalloporphyrin was important for the reaction. The antibody−metalloporphyrin complexes are stable enough to show catalytic activity in the presence of an excess amount of H2O2.