[53] Lipoxygenase from soybeans

Axelrod, Bernard; Cheesbrough, T. M.; Laakso, Simo

doi:10.1016/0076-6879(81)71055-3

Cited by 917 publications

(576 citation statements)

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“…These hormones are involved in a variety of metabolic functions including plant growth and development, senescence, and cellular response to wounding and infections by pathogens (1). Soybeans have three LO isoforms (sLO-1, sLO-2, and sLO-3), which have homologous sequences and molecular weights of ∼96 kDa (9). This study focuses on sLO-1 because of its stability and the fact that most kinetic, structural and spectroscopic studies have involved this isoform.…”

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confidence: 99%

Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

et al. 2003

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Lipoxygenases are non-heme iron enzymes, which catalyze the stereo-and regiospecific hydroperoxidation of unsaturated fatty acids. Spectroscopic studies on soybean lipoxygenase have shown that the ferrous form of the enzyme is a mixture of five-and six-coordinate species (40 and 60%, respectively). Addition of substrate leads to a purely six-coordinate form. A series of mutations in the second coordination sphere (Q697E, Q697N, Q495A, and Q495E) were generated, and the structures of the mutants were solved by crystallography [Tomchick et al. (2001) Biochemistry 40, 7509-7517]. While this study clearly showed the contribution of H-bond interactions between the first and the second coordination spheres in catalysis, no correlation with the coordination environment of the Fe II was observed. A recent study using density-functional theory [Lehnert and Solomon (2002) J. Biol. Inorg. Chem. 8, 294-305] indicated that coordination flexibility, involving the Asn694 ligand, is regulated via H-bond interactions. In this paper, we investigate the solution structures of the second coordination sphere mutants using CD and MCD spectroscopy since these techniques are more sensitive indicators of the first coordination sphere ligation of Fe II systems. Our data demonstrate that the iron coordination environment directly relates to activity, with the mutations that have the ability to form a five-coordinate/six-coordinate mixture being more active. We propose that the H-bond between the weak Asn694 ligand and the Gln697 plays a key role in the modulation of the coordination flexibility of Asn694, and thus, is crucial for the regulation of enzyme reactivity.Lipoxygenases (LOs) 1 are mononuclear non-heme iron dioxygenases that catalyze the stereo-and regiospecific hydroperoxidations of cis,cis-1,4 polyunsaturated pentadienyl containing fatty acids. LOs have been isolated and characterized from numerous mammalian and plant sources and are believed to occur ubiquitously throughout these two phyla (1-3). In mammalian organisms, there are multiple LOs with differing regio-and stereospecificity against their substrate, arachidonic acid (AA). The products of these reactions are further metabolized by an array of enzymes leading to the formation of two major classes of cell effector molecules, leukotrienes and lipoxins, which are mediators in anaphylactic and inflammatory disorders (4, 5). Additionally, LO products are involved in a variety of metabolic functions, including organelle degradation (6), transcription regulation (7), and possibly tumor cell metastasis (8). For plant LOs, the main substrates are linoleic acid (LA) and linolenic acid, which are further metabolized to plant hormones, such as jasmonic acid. These hormones are involved in a variety of metabolic functions including plant growth and development, senescence, and cellular response to wounding and infections by pathogens (1). Soybeans have three LO isoforms (sLO-1, sLO-2, and sLO-3), which have homologous sequences and molecular weights of ∼96 kDa (9). This...

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Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

et al. 2003

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“…LOX activity was measured in the presence of linolenic acid and oxygen according to Axerold et al [13]. The assay consisted of 50 mM Tris-HCl, pH 8.0, 10.2 mM linolenic acid, and various amounts of plant extract brought to a 1 ml final volume.…”

Section: Lipoxygenase Assaymentioning

confidence: 99%

The developmental transition to flowering in Arabidopsis is associated with an increase in leaf chloroplastic lipoxygenase activity

Bañuelos¹,

Argumedo²,

Patel³

et al. 2008

Plant Science

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The developmental transition from vegetative growth to flowering in Arabidopsis is associated with a precipitous decline in the activity of leaf ascorbate peroxidase (APx), an enzymatic scavenger of hydrogen peroxide, and an increase in specific lipid peroxidation leading to the accumulation of 13-hydroperoxy-9,11,15 (Z,E,Z) octadecatrienoic acid (13 HOO-FA). The appearance of this specific isomer suggests that it is of enzymatic origin and may represent the activation of an oxylipin signaling pathway. We thus hypothesized that leaf 13-lipoxygenase (LOX) activity increases at the floral transition and leads to the observed elevation of 13-HOO-FA levels. Leaf protein extracts were prepared from seven distinct life stages of Arabidopsis plants and used to assay for LOX activity. We report that leaf 13-LOX enzymatic activity increases twoto three-fold from the vegetative stage to the immediate post-floral transition stage. We found two forms of LOX activity in cell extracts and show that the higher pH optimum form is the isoenzyme activated. This increase is correlated with a small increase in H 2 O 2 , perhaps resulting from the previously reported decline in leaf APx activity. Very low levels of exogenous H 2 O 2 activate the induced form in vegetative leaf extracts in vitro, suggesting that the floral transition-dependent APx decline and subsequent H 2 O 2 elevation are involved in activating plastid 13-LOX and thus a second messenger oxylipin pathway.

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“…Soybean seeds contain three lipoxygenase isozymes, iipoxygenase-I (L-I), L-2 and L-3 [6]. It has been reported from this laboratory that the L-2 isozyme is responsible for the generation of n-hexanal in soybean homogenates by using mutants lacking lipoxygenase isozymes [4].…”

Section: Introductionmentioning

confidence: 99%

Inhibition by lipoxygenase‐3 ofn‐hexanal generation in soybeans

1991

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Soybean seeds contain three lipoxygenase isozymes. The functions of these lipoxygenase isozymes in n-hexanal generation were investigated by using mutant lines which lack two or three isozymes. In the presence of linoleic acid. the level of n-hexanal produced was highest in the lipoxygenase-I. -3 double deficient line. follovced by the lipoxygenase-2. -3 double deficient, wild type, and lipoxygenase-I, -2, -3 triple deficient lines in that order, and lowest in the lipoxygenase-l, -2 double deficient line. This suggests that lipoxygenase-3 itself cannot produce the n-hexanal precursor and inhibits the n-hexanal generation through other pathways.n-Hexanal generation; Lipoxygenase: Soybean

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[53] Lipoxygenase from soybeans

Cited by 917 publications

References 12 publications

Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

The developmental transition to flowering in Arabidopsis is associated with an increase in leaf chloroplastic lipoxygenase activity

Inhibition by lipoxygenase‐3 ofn‐hexanal generation in soybeans

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[53] Lipoxygenase from soybeans

Cited by 917 publications

References 12 publications

Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

Spectroscopic Characterization of Soybean Lipoxygenase-1 Mutants: the Role of Second Coordination Sphere Residues in the Regulation of Enzyme Activity

The developmental transition to flowering in Arabidopsis is associated with an increase in leaf chloroplastic lipoxygenase activity

Inhibition by lipoxygenase&#x2010;3 ofn&#x2010;hexanal generation in soybeans

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Inhibition by lipoxygenase‐3 ofn‐hexanal generation in soybeans