Improvement of enantioselectivity by immobilized imprinting of epoxide hydrolase from Rhodotorula glutinis

The yeast Rhodotorula glutinis contains an enantioselective, membrane-associated epoxide hydrolase (EH). Partially purified EH was immobilized in a two-step procedure. In the first step, the proteins were derivatized with itaconic anhydride. In the second step, the derivatized proteins were co-polymerized with ethylene glycol dimethacrylate in water-free cyclohexane to form a bioplastic. Before co-polymerization, the derivatized enzyme had been imprinted by substrates or its analogues (called imprinters) in an aqueous phase. After removing the imprinters, an enzyme with rationally modified properties was obtained. This is the first time that the above-mentioned method was successfully performed with a membrane-associated enzyme of the alpha/beta -hydrolase fold family to which EH belongs. The enantioselective conversion of (+/-)-1,2-epoxyoctane was reversed from a preference for (R)-1,2-epoxyoctane to (S)-1,2-epoxyoctane when the enzyme had been imprinted with (S)-1,2-epoxyoctane prior to co-polymerization. The enzymatic reaction was performed in aqueous media. Other benefits of immobilizing EH into a co-polymer were the ease of recycling of the biocatalyst and the separation of biocatalyst and its products. An unexpected benefit was the enhanced enzyme stability. The half-life of the immobilized and imprinted biocatalyst was enhanced at least 7-fold. Most remarkable was that washing the immobilized EH with HCl, followed by washing it with buffer, resulted in about 50% of the residual activity, while native EH completely lost its activity. (C) 2001 Elsevier Science B.V. All rights reserved.