NDLI: Directed modification of the Aspergillus usamii β-mannanase to improve its substrate affinity by in silico design and site-directed mutagenesis

Content Provider	Springer Nature Link
Author	Li, Jianfang Wei, Xihuan Tang, Cunduo Wang, Junqing Zhao, Mei Pang, Qingfeng Wu, Minchen
Copyright Year	2014
Abstract	β-Mannanases (EC 3.2.1.78) can catalyze the cleavage of internal β-1,4-d-mannosidic linkages of mannan backbones, and they have found applications in food, feed, pulp and paper, oil, pharmaceutical and textile industries. Suitable amino acid substitution can promote access to the substrate-binding groove and maintain the substrate therein, which probably improves the substrate affinity and, thus, increases catalytic efficiency of the enzyme. In this study, to improve the substrate affinity of AuMan5A, a glycoside hydrolase (GH) family 5 β-mannanase from Aspergillus usamii, had its directed modification conducted by in silico design, and followed by site-directed mutagenesis. The mutant genes, Auman5A Y111F and Auman5A Y115F, were constructed by megaprimer PCR, respectively. Then, Auman5A and its mutant genes were expressed in Pichia pastoris GS115 successfully. The specific activities of purified recombinant β-mannanases (reAuMan5A, reAuMan5AY111F and reAuMan5AY115F) towards locust bean gum were 152.5, 199.6 and 218.9 U mg−1, respectively. The two mutants were found to be similar to reAuMan5A regarding temperature and pH characteristics. Nevertheless, the K m values of reAuMan5AY111F and reAuMan5AY115F, towards guar gum, decreased to 2.95 ± 0.22 and 2.39 ± 0.33 mg ml−1 from 4.49 ± 0.07 mg ml−1 of reAuMan5A, which would make reAuMan5AY111F and reAuMan5AY115F promising candidates for industrial processes. Structural analysis showed that the two mutants increased their affinity by decreasing the steric conflicts with those more complicated substrates. The results suggested that subtle conformational modification in the substrate-binding groove could substantially alter the substrate affinity of AuMan5A. This study laid a solid foundation for the directed modification of substrate affinities of β-mannanases and other enzymes.
Starting Page	693
Ending Page	700
Page Count	8
File Format	PDF
ISSN	13675435
Journal	Journal of Industrial Microbiology and Biotechnology
Volume Number	41
Issue Number	4
e-ISSN	14765535
Language	English
Publisher	Springer Berlin Heidelberg
Publisher Date	2014-02-04
Publisher Place	Berlin, Heidelberg
Access Restriction	Subscribed
Subject Keyword	Directed modification Aspergillus usamii β-mannanase Substrate affinity In silico design Site-directed mutagenesis Microbiology Biochemistry Inorganic Chemistry Genetic Engineering Biotechnology Bioinformatics
Content Type	Text
Resource Type	Article
Subject	Medicine Bioengineering Applied Microbiology and Biotechnology Biotechnology

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