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Catalytic performance and thermostability of chloroperoxidase in reverse micelle: achievement of a catalytically favorable enzyme conformation.

Journal of industrial microbiology & biotechnology (2010-08-31)
Yali Wang, Jinyue Wu, Xuejiao Ru, Yucheng Jiang, Mancheng Hu, Shuni Li, Quanguo Zhai
ABSTRACT

The catalytic performance of chloroperoxidase (CPO) in peroxidation of 2, 2'-azinobis-(-3 ethylbenzothiazoline-6-sulfononic acid) diammonium salt (ABTS) and oxidation of indole in a reverse micelle composed of surfactant-water-isooctane-pentanol was investigated and optimized in this work. Some positive results were obtained as follows: the peroxidation activity of CPO was enhanced 248% and 263%, while oxidation activity was enhanced 215% and 222% in cetyltrimethylammonium bromide (CTABr) reverse micelle medium and dodecyltrimethylammonium bromide (DTABr) medium, respectively. Thermostability was also greatly improved in reverse micelle: at 40 °C, CPO essentially lost all its activity after 5 h incubation, while 58-76% catalytic activity was retained for both reactions in the two reverse micelle media. At 50 °C, about 44-75% catalytic activity remained for both reactions in reverse micelle after 2 h compared with no observed activity in pure buffer under the same conditions. The enhancement of CPO activity was dependent mainly on the surfactant concentration and structure, organic solvent ratio (V(pentanol)/V(isooctane)), and water content in the reverse micelle. The obtained kinetic parameters showed that the catalytic turnover frequency (k(cat)) was increased in reverse micelle. Moreover, the lower K(m) and higher k(cat)/K(m) demonstrated that both the affinity and specificity of CPO to substrates were improved in reverse micelle media. Fluorescence, circular dichroism (CD) and UV-vis spectra assays indicated that a catalytically favorable conformation of enzyme was achieved in reverse micelle, including the strengthening of the protein α-helix structure, and greater exposure of the heme prosthetic group for easy access of the substrate in bulk solution. These results are promising in view of the industrial applications of this versatile biological catalyst.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
2,2,4-Trimethylpentane, anhydrous, 99.8%
Supelco
2,2,4-Trimethylpentane, analytical standard
Sigma-Aldrich
2,2,4-Trimethylpentane, suitable for HPLC, ≥99%
Sigma-Aldrich
2,2,4-Trimethylpentane, HPLC Plus, for HPLC, GC, and residue analysis, ≥99.5%
Sigma-Aldrich
2,2,4-Trimethylpentane, ReagentPlus®, ≥99%
Sigma-Aldrich
2,2,4-Trimethylpentane, puriss. p.a., ≥99.5% (GC)
Sigma-Aldrich
2,2,4-Trimethylpentane, puriss. p.a., ACS reagent, ≥99.5% (GC)
Sigma-Aldrich
2,2,4-Trimethylpentane, ACS reagent, ≥99.0%
Sigma-Aldrich
Dodecyltrimethylammonium bromide, BioXtra, ~99%
Sigma-Aldrich
Chloroperoxidase from Caldariomyces fumago, buffered aqueous suspension, 1,000-2,000 units/mg protein (E1%/280)
Sigma-Aldrich
Dodecyltrimethylammonium bromide, ≥98%
Sigma-Aldrich
Chloroperoxidase from Caldariomyces fumago, buffered aqueous suspension, ≥3,000 units/mL
Sigma-Aldrich
Dodecyltrimethylammonium chloride, ≥99.0% (AT)
Supelco
Dodecyltrimethylammonium bromide, suitable for ion pair chromatography, LiChropur, ≥98.5% (AT)
Sigma-Aldrich
Dodecyltrimethylammonium chloride, purum, ≥98.0% anhydrous basis (AT)
Sigma-Aldrich
Chloroperoxidase from Caldariomyces fumago, aqueous suspension, brown, >10,000 U/mL
Supelco
Density Standard 692 kg/m3, H&D Fitzgerald Ltd. Quality