Protein Engineering, Vol. 15, No. 2, 147-152,
February 2002
© 2002 Oxford University Press
Modifying the chain-length selectivity of the lipase from Burkholderia cepacia KWI-56 through in vitro combinatorial mutagenesis in the substrate-binding site
1 Laboratory of Molecular Biotechnology, Graduate School of Biological and Agricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 and 2 Chubu Science and Technology Center, Sakae 2-17-22, Naka-ku, Nagoya 460-0008, Japan
The mature lipase of Burkholderia cepacia KWI-56 was synthesized in an enzymatically active form using an in vitro Escherichia coli S30 coupled transcription/translation system by expressing the mature lipase gene (rlip) in the presence of its specific activator. To investigate the substrate specificity of the lipase comprehensively, a large number of mutant lipases were constructed and analyzed in a high throughput manner by combining overlapping PCR and in vitro protein synthesis. In this paper, Phe119 and Leu167, which are located in the acyl portion of the substrate-binding pocket of the lipase of B.cepacia KWI-56, were substituted with six hydrophobic amino acid residues by the in vitro combinatorial mutagenesis. The wild-type and 35 mutant genes amplified by PCR were directly used as templates for the in vitro transcription/translation. The acyl chain-length selectivity of the in vitro expressed lipases against p-nitrophenyl butyrate, p-nitrophenyl caprylate and p-nitrophenyl palmitate, was compared by their relative hydrolysis rates. Two mutant lipases, L167V and F119A/L167M, which showed a significant shift in substrate selectivity were further expressed in vivo and refolded in vitro. It was found that L167V raised its preference for the short-chain ester, whereas F119A/L167M improved its selectivity for the long-chain ester.
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