Abstract
Carbonic anhydrase (CA) is a hydrolase enzyme possessing an active center composed of three histidines (His), zinc(II) (Zn2+), and a hydration water. Here we report the hydrolase-like catalytic activity provided by the oleoyl-histidine (O-His) modified on liposome membranes. O-His was synthesized by the amide bond between oleic acid and His, and was incorporated into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes. The hydrolysis of p-nitrophenylacetate was promoted by O-His modified DOPC liposomes in the presence of Zn2+. The formation of the active center was revealed by UV resonance Raman spectra. We conclude that the liposome membrane surface can be utilized as a platform for artificial hydrolysis reactions by modifying essential ligands inspired from natural enzymes.
Highlights
Carbonic anhydrase (CA) is a typical metalloenzyme that has an active site consisting of zinc(II) (Zn2+), three imidazole residues of L-histidine (His), and a hydration water [1]
CA can promote the hydrolysis of p-nitrophenylacetate (p-NPA)
In the cases of Zn2+ only, and free His + Zn2+, the production rates of p-NP were almost the same, while it was increased by the O-His modified DOPC liposome with Zn2+
Summary
Carbonic anhydrase (CA) is a typical metalloenzyme that has an active site consisting of zinc(II) (Zn2+), three imidazole residues of L-histidine (His), and a hydration water [1]. The active site becomes unstable by immobilization of the enzyme on solid surface To overcome such problems, self-assemblies (micelles and emulsions) have been used to develop technologies with high efficiency and selectivity [6,7,8]. It has been reported that the active site, similar to that of CA, was created by bolaamphiphile [9] This method has a problem: the size and structure of the active center could not be adjusted because of the solid-like rigid surface. It is considered that a liposome membrane interface is a superior platform for constructing the active site like Zn-imidazole complex, since the localization of the ligands can be dynamically controlled depending on the liposome membrane properties (e.g., fluidity and polarity). By adding Zn2+, the creation of the active site like Zn-imidazole complex was evaluated from (i) hydrolysis activity and (ii) varied membrane properties
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