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Compound
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Target Concepts:
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Query: UMLS:C0027960 (
mole
)
21,279
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Lipoxygenases (LOXs) are multifunctional enzymes that catalyze the oxygenation of polyunsaturated fatty acids to hydroperoxy derivatives; they also convert hydroperoxy fatty acids to epoxy leukotrienes and other secondary products. LOXs undergo suicidal inactivation but the mechanism of this process is still unclear. We investigated the mechanism of suicidal inactivation of the rabbit 15-lipoxygenase by [1-(14)C]-(15S,5Z,8Z,11Z,13E)-15-hydroperoxyeicosa-5,8,11,13-tetraenoic acid (15-HpETE) and observed covalent modification of the enzyme protein. In contrast, nonlipoxygenase proteins (bovine serum albumin and human gamma-globulin) were not significantly modified. Under the conditions of complete enzyme inactivation we found that 1.3 +/- 0.2 moles (n = 10) of inactivator were bound per
mole
lipoxygenase
, and this value did depend neither on the enzyme/inactivator ratio nor on the duration of the inactivation period. Covalent modification required active enzyme protein and proceeded to a similar extent under aerobic and anaerobic conditions. In contrast, [1-(14)C]-(15S,5Z,8Z,11Z,13E)-15-hydroxyeicosa-5,8,11,13-tetraenoic acid (15-HETE), which is no substrate for epoxy-leukotriene formation, did not inactivate the enzyme and protein labeling was minimal. Separation of proteolytic cleavage peptides (Lys-C endoproteinase digestion) by tricine SDS-PAGE and isoelectric focusing in connection with N-terminal amino acid sequencing revealed covalent modification of several active site peptides. These data suggest that 15-lipoxygenase-catalyzed conversion of (15S,5Z,8Z,11Z,13E)-15-hydroperoxyeicosa-5,8,11,13-tetraenoic acid to 14,15-epoxy-leukotriene leads to the formation of reactive intermediate(s), which are covalently linked to the active site. Therefore, this protein modification contributes to suicidal inactivation.
...
PMID:Suicidal inactivation of the rabbit 15-lipoxygenase by 15S-HpETE is paralleled by covalent modification of active site peptides. 1254 46
A number of
lipoxygenase
isoenzymes were identified in developing soybean (Glycine max L. Merrill cv Provar) seeds and two have been partially characterized. In a study of
lipoxygenase
level in developing soybean seeds, the enzyme content increased markedly during development. Comparisons of the lipoxygenases from mature soybean seeds and immature seeds by isoelectric focusing, chromatofocusing, sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping identified two categories of isoenzyme. The isoenzymes from immature seeds were found by electron paramagnetic resonance spectroscopy to be isolated at least in part as the high spin iron(III) or active form of the enzyme in contrast to lipoxygenases from mature seeds which were isolated as electron paramagnetic resonance silent, high spin iron(II) species. The discovery of increased levels of lipoxygenases during seed development and their isolation in an active form suggests that the enzyme may play a physiological role during the maturation process. The incorporation of iron-59 from the nutrient medium into
lipoxygenase
during culture of immature seeds was indicative of de novo synthesis of the enzyme. The efficiency of the iron uptake was high, as indicated by the level of radioactivity found in the enzyme (one gram atom of iron per
mole
of
lipoxygenase
).
...
PMID:The lipoxygenases in developing soybean seeds, their characterization and synthesis in vitro. 1666 48
The measurement of the 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) consumption by using ESR allows to follow the anaerobic reaction between linoleic acid (LH) and its 13-hydroperoxide (LOOH) catalysed by
lipoxygenase
. During this reaction, two types of radicals are initially obtained, alkyl (L) and alkoxyl (LO) radicals which formed two types of adducts (LT and OLT) with TEMPOL as characterised by HPLC. The stoichiometry of the adduct formation is two
mole
of TEMPOL consumed for one
mole
of LH and one
mole
of LOOH. Using ESR, the kinetic parameters and the mechanism of the anaerobic reaction have been determined at pH 6.5 for three different lipoxygenases, soybean, horse bean and wheat and compared to the values obtained at pH 9 for soybean
lipoxygenase
. Wheat
lipoxygenase
is very weakly active compared to the other enzymes. An uncompetitive inhibition of the anaerobic reaction catalysed by soybean and horse bean lipoxygenases was observed with 2,6-di-tert-butyl-4-methylphenol (BHT).
...
PMID:Use of ESR and HPLC to follow the anaerobic reaction catalysed by lipoxygenases. 2517 15
Potent and selective inhibitors for phospholipases A
2
(PLA
2
) are useful for studying their intracellular functions. PLA
2
enzymes liberate arachidonic acid from phospholipids activating eicosanoid pathways that involve cyclooxygenase (COX) and
lipoxygenase
(
LOX
) leading to inflammation. Anti-inflammatory drugs target COX and
LOX
; thus, PLA
2
can also be targeted to diminish inflammation at an earlier stage in the process. This paper describes the employment of enzymatic assays, hydrogen/deuterium exchange mass spectrometry (DXMS) and computational chemistry to develop PLA
2
inhibitors. Beta-thioether trifluoromethylketones (TFKs) were screened against human GVIA calcium-independent, GIVA cytosolic and GV secreted PLA
2
s. These compounds exhibited inhibition toward Group VIA calcium-independent PLA
2
(GVIA iPLA
2
), with the most potent and selective inhibitor 3 (OTFP) obtaining an X
I
(50) of 0.0002
mole
fraction (IC
50
of 110nM). DXMS binding experiments in the presence of OTFP revealed the peptide regions of GVIA iPLA
2
that interact with the inhibitor. Molecular docking and dynamics simulations in the presence of a membrane were guided by the DXMS data in order to identify the binding mode of OTFP. Clustering analysis showed the binding mode of OTFP that occupied 70% of the binding modes occurring during the simulation. The resulted 3D complex was used for docking studies and a structure-activity relationship (SAR) was established. This paper describes a novel multidisciplinary approach in which a 3D complex of GVIA iPLA
2
with an inhibitor is reported and validated by experimental data. The SAR showed that the sulfur atom is vital for the potency of beta-thioether analogues, while the hydrophobic chain is important for selectivity. This work constitutes the foundation for further design, synthesis and inhibition studies in order to develop new beta-thioether analogues that are potent and selective for GVIA iPLA
2
exclusively.
...
PMID:Computer-aided drug design guided by hydrogen/deuterium exchange mass spectrometry: A powerful combination for the development of potent and selective inhibitors of Group VIA calcium-independent phospholipase A
2
. 2732 Jun 59
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