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Two arginine residues in the substrate pocket predominantly control the substrate selectivity of thiocyanate hydrolase
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Description
Thiocyanate hydrolase (SCNase) of Thiobacillus thioparus THI115 is a cobalt (Co)-containing enzyme that catalyzes the hydrolysis of thiocyanate (SCN⁻), a major component of wastewater from coke oven factories, to carbonyl sulfide and ammonia. Although SCNase exhibits high structural similarities to Co-type nitrile hydratase (NHase), including a unique Co³⁺ catalytic center with two oxidized Cys ligands, both SCNase and NHase exclusively catalyze only their own substrates. Based on the differences in the substrate-binding pockets of these enzymes, βArg90 and γArg136 of SCNase, with side chains extending toward the pocket, were separately substituted with Phe and Trp, the corresponding residues, respectively, in Co-type NHase. Both SCNase βArg90 and SCNase γArg136 mutants showed no SCN⁻ hydrolysis activity but did catalyze the hydration of nitriles. The estimated kcat values (∼2 s⁻¹) corresponded to approximately 0.2% of that of Co-type NHase for nitrile hydration and approximately 3% of that of wild-type SCNase for SCN⁻ hydrolysis. The crystal structure of SCNase γR136W is essentially identical to that of the wild-type, including the Co³⁺ center having Cys oxidations; the size of the substrate pocket was enlarged because of conformational changes on the side chains of the mutated residue. Discussion of the difference in the environments around the substrate-binding pockets among the wild-type and mutant SCNases and Co-type NHase strongly suggests that βArg90 and γArg136, positioned at the top of the Co³⁺ center, predominantly control the substrate selectivity of SCNase.
Journal
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- Journal of bioscience and bioengineering
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Journal of bioscience and bioengineering 116 (1), 22-27, 2013-07
Suita : Society for Biotechnology
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Details 詳細情報について
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- CRID
- 1520291855081867904
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- NII Article ID
- 110009634740
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- NII Book ID
- AA11307678
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- ISSN
- 13891723
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- NDL BIB ID
- 024715365
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- PubMed
- 23453853
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- Text Lang
- en
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- Article Type
- journal article
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- NDL Source Classification
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- ZP15(科学技術--化学・化学工業--醗酵・微生物工学)
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- Data Source
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- NDL Search
- Crossref
- CiNii Articles
- KAKEN
- OpenAIRE