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Crystal Structure and Functional Characterization of a Xylose Isomerase (PbXI) from the Psychrophilic Soil Microorganism, Paenibacillus sp.

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Title
Crystal Structure and Functional Characterization of a Xylose Isomerase (PbXI) from the Psychrophilic Soil Microorganism, Paenibacillus sp.
Other Titles
알래스카 토양 미생물 유래 xylose isomerase 효소의 구조와 기능 연구
Authors
Park, Sun-Ha
Kwon, Sunghark
Lee, Chang Woo
Kim, Chang Min
Jeong, Chang Sook
Kim, Kyung-Jin
Hong, Jong Wook
Kim, Hak Jun
Park, Hyun Ho
Lee, Jun Hyuck
Subject
Biotechnology & Applied Microbiology; Microbiology
Keywords
Paenibacillus species; X-ray crystallography; cold-active protein; crystal structure; xylose isomerase
Issue Date
2019-02
Citation
Park, Sun-Ha, et al. 2019. "Crystal Structure and Functional Characterization of a Xylose Isomerase (PbXI) from the Psychrophilic Soil Microorganism, Paenibacillus sp.". JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY, 29(2): 244-255.
Abstract
Xylose isomerase (XI; E.C.5.3.1.5) catalyzes the isomerization of xylose to xylulose, which can be used to produce bioethanol through fermentation. Therefore, XI has recently gained attention as a key catalyst in the bioenergy industry. Here, we identified, purified, and characterized a XI (PbXI) from the psychrophilic soil microorganism, Paenibacillus sp. R4. Surprisingly, activity assay results showed that PbXI is not a cold-active enzyme, but displays optimal activity at 60 degrees C. We solved the crystal structure of PbXI at 1.94-angstrom resolution to investigate the origin of its thermostability. The PbXI structure shows a (beta/alpha)(8)-barrel fold with tight tetrameric interactions and it has three divalent metal ions (CaI, CaII, and CaIII). Two metal ions (CaI and CaII) located in the active site are known to be involved in the enzymatic reaction. The third metal ion (CaIII), located near the beta 4-alpha 6 loop region, was newly identified and is thought to be important for the stability of PbXI. Compared with previously determined thermostable and mesophilic XI structures, the beta 1-alpha 2 loop structures near the substrate binding pocket of PbXI were remarkably different. Site-directed mutagenesis studies suggested that the flexible beta 1-alpha 2 loop region is essential for PbXI activity. Our findings provide valuable insights that can be applied in protein engineering to generate low-temperature purpose-specific XI enzymes.
URI
https://repository.kopri.re.kr/handle/201206/10876
DOI
http://dx.doi.org/10.4014/jmb.1810.10057
Appears in Collections  
2019-2019, Development of potential candidates as antibiotics based on polar genetic resources (19-19) / Lee, Jun Hyuck (PE19210)
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