Cloned (Comment) | Organism |
---|---|
recombinant expression of His-tagged enzyme in Escherichia coli strain BL21 Star | Rippkaea orientalis PCC 8801 |
Crystallization (Comment) | Organism |
---|---|
purified recombinant wild-type enzyme CspLOX2, sitting drop vapor diffusion method, from well solution of 10% PEG 4000, 0.1 M MES/imidazole pH 6.5, 20% glycerol and 0.02% alcohols (1,6-hexanediol, 1-butanol, 1,2-propanediol, 2-propanol, 1,4-butanediol, and 1,3-propanediol), 10 days, purified recombinant CspLOX2 mutant enzymes by hanging drop vapour diffusion method, from well solution of 12.5-15 PEG 4000, 8-12% glycerol, 0.1 M MES/imidazole pH 6.1, and 0-600 mM NaCl, X-ray diffraction structure determination and analysis at 1.8 A resolution. Crystals of a CspLOX2 substrate complex are not obtained | Rippkaea orientalis PCC 8801 |
Protein Variants | Comment | Organism |
---|---|---|
A300G | site-directed mutagenesis, structure comparison with wild-type enzyme, enantioselectivity towards formation of 9R- and 13S-hydroperoxyoctadeca-9,12-dienoate is increased compared to the wild-type enzyme | Rippkaea orientalis PCC 8801 |
I296A | site-directed mutagenesis, structure comparison with wild-type enzyme, the stereospecificity of the mutant activity is inverted compared to the wild-type enzyme | Rippkaea orientalis PCC 8801 |
L258V | site-directed mutagenesis, structure comparison with wild-type enzyme, the mutation only slightly affects the enzyme activity | Rippkaea orientalis PCC 8801 |
L502V | site-directed mutagenesis, structure comparison with wild-type enzyme, enantioselectivity towards formation of 9R- and 13S-hydroperoxyoctadeca-9,12-dienoate is increased compared to the wild-type enzyme | Rippkaea orientalis PCC 8801 |
L506V | site-directed mutagenesis, structure comparison with wild-type enzyme, the stereospecificity of the mutant activity is inverted compared to the wild-type enzyme | Rippkaea orientalis PCC 8801 |
additional information | modulating the cavity volume around the pentadiene system of linoleic acid shifts the product formation towards 9S-, 9R-, 13S- or 13R-hydroperoxides in correlation with the site of mutation, thus decreasing the amount of the bis-allylic 11R-hydroperoxide | Rippkaea orientalis PCC 8801 |
Metals/Ions | Comment | Organism | Structure |
---|---|---|---|
Fe3+ | non-heme iron, required. The catalytic non-heme iron, deeply buried in the CspLOX2 active site, is coordinated by three invariant histidines (His257, His262, His449), Asn453 and the carboxy group of the C-terminal Ile569. The sixth ligand of the octahedrally coordinated iron, which is positioned towards the putative substrate binding channel, is a water (Fe2+-H2O) or hydroxide molecule (Fe3+-OH) acting as a catalytic base for hydrogen abstraction during catalysis, coordination of the iron cofactor, overview | Rippkaea orientalis PCC 8801 |
Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
---|---|---|---|---|---|---|
linoleate + O2 | Rippkaea orientalis PCC 8801 | - |
(9Z,12Z)-(11S)-11-hydroperoxyoctadeca-9,12-dienoate | - |
? |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Rippkaea orientalis PCC 8801 | B7JX99 | - |
- |
Purification (Comment) | Organism |
---|---|
recombinant His-tagged enzyme from Escherichia coli strain BL21 Star by nickel affinity chromatography, gel filtration, and ultrafiltration | Rippkaea orientalis PCC 8801 |
Reaction | Comment | Organism | Reaction ID |
---|---|---|---|
linoleate + O2 = (9Z,12Z)-(11S)-11-hydroperoxyoctadeca-9,12-dienoate | the LOX reaction is always catalyzed at a 1Z,4Z-pentadiene system of a polyunsaturated fatty acid. In the initial step, a hydrogen atom is abstracted from the central bis-allylic methylene group by the non-heme iron or in few cases manganese in the active site. During this rate-limiting step, Fe(III) is reduced to Fe(II) in the former case and a substrate radical is formed which rapidly delocalizes over the five carbon unit. Addition of dioxygen yields a peroxyl radical, which is finally reduced to the hydroperoxide product | Rippkaea orientalis PCC 8801 |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
linoleate + O2 | - |
Rippkaea orientalis PCC 8801 | (9Z,12Z)-(11S)-11-hydroperoxyoctadeca-9,12-dienoate | - |
? | |
linoleate + O2 | analysis of substrate conformation and environment, overview | Rippkaea orientalis PCC 8801 | (9Z,12Z)-(11S)-11-hydroperoxyoctadeca-9,12-dienoate | - |
? |
Synonyms | Comment | Organism |
---|---|---|
CspLOX2 | - |
Rippkaea orientalis PCC 8801 |
lipoxygenase 2 | - |
Rippkaea orientalis PCC 8801 |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
iron cofactor | coordination of the iron cofactor, overview | Rippkaea orientalis PCC 8801 |
General Information | Comment | Organism |
---|---|---|
additional information | residues around the active site direct dioxygen to a preferred carbon atom and stereo configuration in the substrate fatty acid. An active site clamp fixing the pentadiene system of the substrate together with steric shielding controls the stereo- and regiospecific positioning of dioxygen at all positions of the reacting pentadiene system of substrate fatty acids. The restricted space in the kink region is required for effective 11-HPODE formation by CspLOX2, as a tight and kinked substrate-binding channel might induce slight distorsions in the reacting pentadiene system, thus altering the reactivity, structure-activity analysis, modeling, overview. Crucial residues in the direct environment of the narrow active site that form a clamp-like structure include Leu304, Leu258, Ile296, Ala300, Leu502 and Leu506. Molecular dynamics simulations support a major role of steric shielding of active site clamp | Rippkaea orientalis PCC 8801 |