Chemical modification of the protein molecules improve their activity in organic solvents

Abstract

Abstract Enzymatic activities in organic solvents were studied to evaluate their potential for oxidation of components of the asphaltene fraction of crude oils. Horseradish peroxidase and cytochrome c were chemically modified in order to increase their surface hydrophobicity. Deglycolsylation, benzyl- and poly(ethylene glycol)-modifications of horseradish peroxidase were tested in organic solvents, such as toluene, benzene, methylene chloride and diethylether. The biocatalytic activity of horseradish peroxidase in toluene was enhanced up to 16 times by the poly(ethylene glycol) modification. In some water-immiscible solvents such as toluene, benzene and diethylether, and in a system containing 80% of water-miscible organic solvent, the activity was correlated with the superficial hydrophobicity of the enzyme. Cytochrome c from horse heart was able to catalyze the oxidation of thiophenes and organosulfides. As in the case of horseradish peroxidase, the poly(ethylene glycol)-modified cytochrome c showed higher activity than the unmodified protein in a medium containing 90% of tetrahydrofuran. In some cases, the chemical modification can improve the protein stability in organic solvent systems.