Yilmaz, F.

Process Biochem. 2018, 72, 71-78, 10.1016/j.procbio.2018.06.005

Carbonic anhydrase (carbonic dehydratase) (CA) is a metalloenzyme that contains zinc (Zn2+) ion in its active site. CA catalyzes the reversible conversion of carbon dioxide and water to bicarbonate and protons. Zn2+ ions, which are present in the active site of the enzyme, interact with the substrate molecules directly and cause catalytic effect. In this study, a nano-enzyme system was designed in aqueous solutions at room temperature and under nitrogen atmosphere to use the CA enzyme without any pre-treatment and deformation in its structure. The novel concept ANADOLUCA (AmiNo Acid (monomer) Decorated and Light Underpinning Conjugation Approach) was used for this process, nano CA enzyme of size 93 nm was synthesized. The activity of the synthesized nano CA was measured following the change in absorbance during the conversion of 4-nitrophenylacetate (NPA) to 4-nitrophenylate ion at 348 nm for a period of 10 min at 25 °C compared with free CA enzyme. Km and Vmax values for nano CA enzyme were found to be 0.442 mM and 1.6 × 10−3 mM min-1, respectively, whereas Km and Vmax values for free CA were found to be 0.471 mM and 1.5 × 10−3 mM min-1, respectively. In addition to these, the Zn2+ ion present in the active site of the nano CA enzyme was replaced by rodium metal. This nanorodium-substituted CA has been investigated as a new reductase enzyme for the stereoselective hydrogenation of olefins. Then, the Zn2+ ion in the active site of the nano CA enzyme was replaced with manganese metal to enhance the enzyme structure, thereby gaining characteristics of peroxidase. This newly synthesized nano manganese-substituted CA enzyme was investigated for its role as a peroxidase, which could be an alternative for hydrogen peroxidases.

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.