A substrate serves as a hydrogen atom donor in the enzyme-initiated catalytic mechanism of dual positional specific maize lipoxygenase-1

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Title
A substrate serves as a hydrogen atom donor in the enzyme-initiated catalytic mechanism of dual positional specific maize lipoxygenase-1
Author(s)
T Huon; S Jang; K Cho; R Rakwal; J C Woo; I Kim; Seung-Wook Chi; O Han
Bibliographic Citation
Bulletin of Korean Chemical Society, vol. 30, no. 4, pp. 917-923
Publication Year
2009
Abstract
The maize lipoxgyenase-1 is a non-traditional dual positional specific enzyme and the reaction proceeds via enzyme-initiated catalysis. Bioinformatic analysis indicated that the maize lipoxygenase-1 is structurally more similar to soybean LOX1 than pea LOXN2 in that it has an additional external loop (residues 318-351) in the carboxy-terminal catalytic domain. We analyzed the dependence of product distribution on concentration of linoleic acid and monitored the formation of hydroperoxyoctadecadienoic acid as a function of enzyme concentration. Product distribution was strongly influenced by substrate concentration, such that kinetically-controlled regioisomers were enriched and thermodynamically-controlled regioisomers were depleted at high substrate concentration. Kinetic studies indicated that the formation of hydroperoxyoctadecadienoic acid saturated rapidly in an enzyme concentration-dependent manner, which implied that reactivation by reoxidation of inactive Fe(II) failed to occur. Our results support the previously proposed enzyme-initiated catalytic mechanism of the maize lipoxgyenase-1 and reveals that a substrate molecule serves as a hydrogen atom donor in its enzyme-initiated catalysis.
Keyword
Dual positional lipoxygenaseEnzyme-initiated mechanismKinetic controlRadical mechanismThermodynamic control
ISSN
0253-2964
Publisher
Wiley
DOI
http://dx.doi.org/10.5012/bkcs.2009.30.4.917
Type
Article
Appears in Collections:
Division of Biomedical Research > 1. Journal Articles
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