Binding of Imidazole Stabilizes Low-spin State of Heme Iron in Dual-Substrate-Specific Rice Allene Oxide Synthase-1

Kinetic studies have indicated that imidazole is a competitive inhibitor of rice allene oxide synthase‐1 with K i of 34.9, 14.3, 40.3, and 23.3 mM for 13(S)‐HPODE, 13(S)‐HPOTE, 9(S)‐HPODE, and 9(S)‐HPOTE as substrates, respectively. Imidazole‐free rice allene oxide synthase‐1 has a Soret absorbance...

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Published inBulletin of the Korean Chemical Society Vol. 36; no. 8; pp. 2015 - 2019
Main Authors Yoeun, Sereyvath, Sukhanov, Andrey, Han, Oksoo
Format Journal Article
LanguageEnglish
Published Weinheim Wiley-VCH Verlag GmbH & Co. KGaA 01.08.2015
Wiley‐VCH Verlag GmbH & Co. KGaA
대한화학회
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ISSN1229-5949
0253-2964
1229-5949
DOI10.1002/bkcs.10388

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Summary:Kinetic studies have indicated that imidazole is a competitive inhibitor of rice allene oxide synthase‐1 with K i of 34.9, 14.3, 40.3, and 23.3 mM for 13(S)‐HPODE, 13(S)‐HPOTE, 9(S)‐HPODE, and 9(S)‐HPOTE as substrates, respectively. Imidazole‐free rice allene oxide synthase‐1 has a Soret absorbance maximum at 393 nm and occupied high‐spin (g = 6.0) and low‐spin (g = 2.39, 2.24, 1.93) states in the ratio 1:10, as detected by EPR spectroscopy, while in the presence of imidazole the occupancy of the low‐spin state increased to 100%. The results support the hypothesis that imidazole competes with the substrate of allene oxide synthase‐1 for binding to the sixth position of heme iron(III) and that binding of imidazole stabilizes the low‐spin state. The role of detergent binding and implications for the mechanism by which allene oxide synthase‐1 cleaves the RO‐OH bond are discussed.
Bibliography:National Research Foundation - No. (2011-0008591)
istex:DC5D683527D0A20A3B6B18811C2B7C428B621B61
ark:/67375/WNG-7NDBSGCS-X
ArticleID:BKCS10388
G704-000067.2015.36.8.020
http://onlinelibrary.wiley.com/doi/10.1002/bkcs.10388/abstract
ISSN:1229-5949
0253-2964
1229-5949
DOI:10.1002/bkcs.10388