Regio- and stereochemistry of the dioxygenation reaction catalyzed by (S)-type lipoxygenases or by the cyclooxygenase activity of prostaglandin H synthases

Lehmann, Wolf D.

doi:10.1016/0891-5849(94)90149-x

Cited by 44 publications

(29 citation statements)

References 79 publications

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“…Earlier investigations suggested that the spatial arrangement of the substrate fatty acid at the active site of lipoxygenases appears to be crucial for the positional specificity of lipoxygenases (Hamberg & Samuelsson, 1967;Kü hn et al, 1986;Lehmann, 1994). Our calculations on the alignment of rather bulky Phe at this position (Funk et al, 1990;Yoshimoto et al, 1990;DeMarzo et al, 1992).…”

Section: Discussionmentioning

confidence: 89%

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Phenylalanine 353 is a Primary Determinant for the Positional Specificity of Mammalian 15-Lipoxygenases

Borngräber

Kuban

Anton

et al. 1996

Journal of Molecular Biology

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Section: Discussionmentioning

confidence: 89%

“…This is primarily due to the lack of X-ray data on the three-dimensional structure of mammalian lipoxygenases. However, several lines of experimental evidence have suggested that the spatial arrangement of the substrate at the active site of the enzyme appears to be important Lehmann, 1994).…”

Section: Introductionmentioning

confidence: 99%

Phenylalanine 353 is a Primary Determinant for the Positional Specificity of Mammalian 15-Lipoxygenases

Borngräber

Kuban

Anton

et al. 1996

Journal of Molecular Biology

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“…Ratios of S and R were determined by CP-HPLC (Insets). substrate is bound inversely at the active site, so the carboxylate group may penetrate into the substrate-binding pocket (9)(10)(11)(12). According to this inverse-orientation hypothesis, the stereochemistry of linoleate 9-lipoxygenation is straightforward and there is no need to postulate conformational changes of either substrate or enzyme.…”

Section: Discussionmentioning

confidence: 99%

“…However, for now, it is not clear which steric factors will favor a [9,10,11]-allyl radical leading to 13-HPODE formation and which will favor a [11,12,13]-allyl radical (9-HPODE formation). It might be possible that the H608V exchange reported here may alter the overall substrate configuration in such a way that the formation of a [11,12,13]-allyl radical becomes sterically favored, which would lead to 9-HPODE formation.…”

Section: Discussionmentioning

confidence: 99%

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Conversion of cucumber linoleate 13-lipoxygenase to a 9-lipoxygenating species by site-directed mutagenesis

Hornung

Walther²,

Kühn³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

135

107

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Multiple lipoxygenase sequence alignments and structural modeling of the enzyme͞substrate interaction of the cucumber lipid body lipoxygenase suggested histidine 608 as the primary determinant of positional specificity. Replacement of this amino acid by a less-space-filling valine altered the positional specificity of this linoleate 13-lipoxygenase in favor of 9-lipoxygenation. These alterations may be explained by the fact that H608V mutation may demask the positively charged guanidino group of R758, which, in turn, may force an inverse head-to-tail orientation of the fatty acid substrate. The R758L؉H608V double mutant exhibited a strongly reduced reaction rate and a random positional specificity. Trilinolein, which lacks free carboxylic groups, was oxygenated to the corresponding (13S)-hydro(pero)xy derivatives by both the wild-type enzyme and the linoleate 9-lipoxygenating H608V mutant. These data indicate the complete conversion of a linoleate 13-lipoxygenase to a 9-lipoxygenating species by a single point mutation. It is hypothesized that H608V exchange may alter the orientation of the substrate at the active site and͞or its steric configuration in such a way that a stereospecific dioxygen insertion at C-9 may exclusively take place.Lipoxgenases (LOXs; linoleate:oxygen oxidoreductase; EC 1.13.11.12) are widely distributed in the plant and animal kingdom (1, 2). They constitute a family of nonheme ironcontaining dioxygenases that catalyze the regio-and stereoselective dioxygenation of polyenoic fatty acids forming hydroperoxy derivatives (3). In mammals, LOXs are classified according to their positional specificity of arachidonic acid oxygenation (2, 4). Because arachidonic acid either is not present in higher plants or is a minor constituent of cellular lipids, plant LOXs are classified into 9-and 13-LOXs with respect to their positional specificity of linoleic acid (LA) oxygenation (5). Recently, a more comprehensive classification of plant LOXs has been proposed based on the comparison of their primary structures (6).The positional specificity of LOXs is a result of two catalytic processes. (i) Regio-and stereospecific hydrogen removal; with substrate fatty acids containing several doubly allylic methylenes such as linolenic acid, arachidonic acid, or eicosapentaenoic acid hydrogen abstraction from two, three, or four doubly allylic methylenes, respectively, is possible. (ii) Regio-and stereospecific oxygen insertion: when hydrogen is abstracted from a certain doubly allylic methylene, molecular oxygen can be introduced either at the [ϩ2] or at the [Ϫ2] position (Fig. 1). Thus, a fatty acid containing three doubly allylic methylenes such as arachidonic acid can be oxygenated by a LOX to six regioisomeric hydroperoxy derivatives (HPETEs), namely 15-and 11-HPETE (originating from C-13 hydrogen removal), 12-and 8-HPETE (C-10 hydrogen removal), and 9-and 5-HPETE (C-7 hydrogen removal). Experiments on mammalian 12-and 15-LOXs indicated that the site of hydrogen abstraction can be altered when critical ...

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Analysis of Lipoxygenase Activity and Products

Gardner

2001

Current Protocols in Food Analytical Chemistry

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Lipoxygenase (LOX), a non-heme iron protein, catalyzes the dioxygenation of methylene-interrupted (Z,Z)-pentadiene fatty acids to furnish conjugated hydroperoxydiene fatty acids. In the plant kingdom, the substrate fatty acids are usually linoleic acid or linolenic acids. However, plant LOXs, like their animal counterparts, are fully capable of oxidizing animal polyunsaturated fatty acids such as arachidonic acid. Most LOXs can oxidize glyceride polyunsaturated fatty acids as well. Linoleic acid usually serves as the model substrate. Hydroperoxide products of linoleic acid are usually either 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13S-HPODE), 9(S)-hydroperoxy-10(E),12(Z)octadecadienoic acid (9S-HPODE), or both (Figure C4.2.1). Other isomers have been found as LOX products, but usually the minor amounts of (E,E)-diene isomers observed are racemic, indicating that they arise from the rearrangement of fatty acid peroxyl radicals formed by either enzymic or autooxidation processes. Although LOX activity is important to the plant's defense against pathogens, there are negative aspects of the enzyme in foods. LOX activity and the resulting fatty acid hydroperoxide products initiate free radical chains that modify proteins (particularly residues of Trp, His, Cys, Tyr, Met, and Lys) as well as vitamins or their precursors (e.g., carotene and tocopherol). Evidence of such free radical reactions is often visibly observed as loss of carotenoid/chlorophyll pigments in improperly blanched frozen foods. Another consequence of these free radical reactions is the development of potent off-flavors, many of which originate from decomposition of the fatty acid hydroperoxide products. As seen in Figure C4.2.1, there are two obvious methods of readily measuring LOX activity, that is, by oxygen uptake and ultraviolet (UV) absorbance of the conjugated hydroperoxy-diene product. Basic Protocol 1 describes the polarographic measurement Contributed by Harold W. Gardner

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Regio- and stereochemistry of the dioxygenation reaction catalyzed by (S)-type lipoxygenases or by the cyclooxygenase activity of prostaglandin H synthases

Cited by 44 publications

References 79 publications

Phenylalanine 353 is a Primary Determinant for the Positional Specificity of Mammalian 15-Lipoxygenases

Phenylalanine 353 is a Primary Determinant for the Positional Specificity of Mammalian 15-Lipoxygenases

Conversion of cucumber linoleate 13-lipoxygenase to a 9-lipoxygenating species by site-directed mutagenesis

Analysis of Lipoxygenase Activity and Products

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