Singh SK, Heng C, Braker JD, Chan VJ, Lee CC, Jordan DB, Yuan L, Wagschal K. Directed evolution of GH43 β-xylosidase XylBH43 thermal stability and L186 saturation mutagenesis.
J Ind Microbiol Biotechnol 2013;
41:489-98. [PMID:
24292973 DOI:
10.1007/s10295-013-1377-0]
[Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 10/24/2013] [Indexed: 11/28/2022]
Abstract
Directed evolution of β-xylosidase XylBH43 using a single round of gene shuffling identified three mutations, R45K, M69P, and L186Y, that affect thermal stability parameter K(t)⁰·⁵ by -1.8 ± 0.1, 1.7 ± 0.3, and 3.2 ± 0.4 °C, respectively. In addition, a cluster of four mutations near hairpin loop-D83 improved K(t)⁰·⁵ by ~3 °C; none of the individual amino acid changes measurably affect K(t)⁰·⁵. Saturation mutagenesis of L186 identified the variant L186K as having the most improved K(t)⁰·⁵ value, by 8.1 ± 0.3 °C. The L186Y mutation was found to be additive, resulting in K(t)⁰·⁵ increasing by up to 8.8 ± 0.3 °C when several beneficial mutations were combined. While k cat of xylobiose and 4-nitrophenyl-β-D-xylopyranoside were found to be depressed from 8 to 83 % in the thermally improved mutants, K(m), K(ss) (substrate inhibition), and K(i) (product inhibition) values generally increased, resulting in lessened substrate and xylose inhibition.
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