Comparative Study on the Catalytic Hydration of Carbon Dioxide by Catalysts that Mimic Carbonic Anhydrase Prepared with Zinc Salts

Abstract

Recently, a new catalyst that mimics carbonic anhydrase (CA) was constructed by the self‐assembly of histidyl bolaamphiphilic molecules and a Zn ion cofactor. The catalytic Zn ion complex in a tetrahedral coordination geometry is composed of self‐organized histidyl imidazoles and a single hydroxide ion. However, the Znhydroxide coordination, the key structure of the catalytic analogue, is disturbed by the pairing anion of the Zn salt. Here, the performances of the CA‐mimicking catalysts prepared from various Zn salts were examined along with CO2 hydration. Among the Zn salts with different anions, Zn(OH)2 showed the highest catalytic performance with increased CO2 hydrolysis activity. Spectroscopic and thermodynamic analyses proved the formation of histidineZnhydroxide coordination with a lowered activation energy if Zn(OH)2 was used. With regard to the anion interaction with the Zn ion, the catalytic performance is inversely proportional to the solution dissociation energy of the Zn salt.

Effects of transition metal ions on the catalytic activity of carbonic anhydrase mimics

“…This turning over of catalytic efficiency is supposed to be caused by inhibition of the chloride ion, a counter ion of the metal salt. In our previous study, the efficiency decay was mainly induced by the binding of the pairing anion to the Zn cofactor, which disturbed catalytically active Zn OH coordination [27]. The relatively weak concentration dependency of the Co-, Cd-and Ni-catalysts implied that the pairing anions of these metal cations would interfere little with the metal-hydroxyl coordination, although few catalytic active sites were created on the histidyl bolaamphiphile self-assembly.…”

Peroxidase-like oxidative activity of a manganese-coordinated histidyl bolaamphiphile self-assembly

“…We previously reported the preparation of solid self-assemblies of bolaamphiphiles containing tyrosine or histidine segments, and the constructed suprastructure exhibited unusual biochemical properties such as enhanced photo energy transfer and high catalytic activity. 18,19 The self-assembly of a histidyl bolaamphiphile was particularly useful for imitating an enzyme since histidine imidazoles can coordinate to various transition metal ions to form metalloenzyme analogues. We previously demonstrated the preparation of catalytic analogues mimicking the active site of carbonic anhydrase using a histidyl bolaamphiphile self-assembly coordinated to a Zn ion cofactor.…”

Hydrolase-Like Activity Provided by Zinc(II) and Oleoyl-Histidine at Liposome Membrane Surface

“…Zn(OAc) 2 was selected as a source of Zn 2+ , according to literature [28]. The solutions of O-His modified DOPC liposome (total amphiphile content: 2.5 mM) and Zn(OAc) 2 were mixed with a mole ratio of O-His/Zn 2+ = 3/1, and the mixture was incubated at 25 • C for 2 h. After incubation, Raman spectra were measured using a confocal Raman microscopy (LabRAM HR-800, Horiba, Ltd., Kyoto, Japan).…”