Lipoxygenase‐2 Oxygenates Storage Lipids in Embryos of Germinating Barley

Holtman, W.; Vredenbregt-Heistek, J.; Schmitt, Nathalie; Feußner, Ivo

doi:10.1111/j.1432-1033.1997.00452.x

Cited by 48 publications

(48 citation statements)

References 25 publications

(23 reference statements)

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“…5 where the total amount of products obtained after 2 h enzymatic reaction was analysed by GC-MS. It can be assumed that the two isoenzymes in previous investigations 10,11,21 were not fully separated and biotransformation with partially purified LOX1 and LOX2 led to a lower regioselectivity of both isoenzymes. Additionally autoxidation also contributes to lower regioselectivity.…”

Section: Regioselectivity Of Partial Purified Lox Isoenzymesmentioning

confidence: 99%

“…LOX1 was purified 7.1 fold while LOX2 was purified 8.0 fold. Holtman et al 10 working with a 1.6 × 30 cm hydroxylapatite column obtained two peaks that were purified 3.5 fold (first peak -LOX1) and 11 fold (second peak -LOX2). According to these authors the low purification factors obtained were caused by the unstable character of these LOX.…”

Section: Hydroxylapatite Chromatography Versus Isoelectric Focussingmentioning

confidence: 99%

“…These peaks are supposed to represent the (E,E) isomers from the enzymatically formed 9-(E,Z)-HPODE and 13-(Z,E)-HPODE. According to Holtmann et al 10 LOX1 derived HPODE showed a (13ZE:13EE:9EZ:9EE) ratio of (1:18:59:22) and LOX2 with a ratio of (51: 18:11:20). These high amounts of (E,E) isomers could not be confirmed in our experiments (data not shown).…”

Section: Stereoselectivity Of Partially Purified Lox Isoenzymesmentioning

confidence: 99%

“…These data are in good agreement with results described in other publications. For germinated barley a ratio of 9-HPODE:13-HPODE of 80:20 11,21 and 81:19 10 for LOX1 and a ratio of 37:63 21 , Table I. Purification steps of LOX isoenzymes from 2.09 g (dry matter) ground green malt using hydroxylapatite chromatography.…”

Section: Regioselectivity Of Partial Purified Lox Isoenzymesmentioning

confidence: 99%

“…Flavour active compounds found in wort or beer, such as hexanal, hexenal, trans-2-nonenal and 2,4-decadienal, originate from these hydroperoxides 17 . While lipoxygenase 1 (LOX1) is already present in barley and catalyses the formation of (S)-9-hydroperoxy-10E,12Z-octadecadienoic acid ((S)-9-HPODE), lipoxygenase 2 (LOX2) is formed during germination and catalyses the formation of (S)-13-hydroperoxy-9Z,11E-octadecadienoic acid ((S)-13-HPODE) when reacting with linoleic acid 4,10 . These facts suggest that these isoenzymes play different roles during barley germination.…”

Section: Introductionmentioning

confidence: 99%

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Regio- and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2

Almeida

Garbe

Nagel

et al. 2005

Journal of the Institute of Brewing

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The characterisation of lipoxygenases LOX1 and LOX2 and hydroperoxyoctadecadienoic acid (HPODE) degrading enzymes from barley green malt is reported. Hydroxylapatite chromatography (HAC) and isoelectric focussing (IEF) were performed to separate and purify LOX isoenzymes. The regio-and stereoselectivity of LOX1 and LOX2 towards linoleic acid as substrate was characterised. HAC purified isoenzyme LOX1 showed a 9-HPODE:13-HPODE ratio of 75:25 and LOX2 a ratio of 39:61. IEF separated LOX1 and LOX2 transformed linoleic acid to 9-:13-HPODE ratios of 90:10, and 13:87, respectively. 9-HPODE stereoisomers from LOX1 exhibited a S:R ratio of 93:7 and 13-HPODE from LOX2 a S:R ratio of 89:11. However, the minor regioisomers were analysed with S:R = 48:52 (LOX1, 13-HPODE) and 40:60 (LOX2, 9-HPODE). These results indicate a complete LOX isoenzyme separation by IEF. Hydroperoxide-metabolising enzymes, which were investigated in the IEF fractions, did not interfere with the dual position specificities of LOX isoenzymes.

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Section: Regioselectivity Of Partial Purified Lox Isoenzymesmentioning

confidence: 99%

Section: Hydroxylapatite Chromatography Versus Isoelectric Focussingmentioning

confidence: 99%

Section: Stereoselectivity Of Partially Purified Lox Isoenzymesmentioning

confidence: 99%

Section: Regioselectivity Of Partial Purified Lox Isoenzymesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Regio- and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2

Almeida

Garbe

Nagel

et al. 2005

Journal of the Institute of Brewing

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Characterization of a 13-lipoxygenase from virgin olive oil and oil bodies of olive endosperms

Georgalaki¹,

Bachmann

Sotiroudis

et al. 1998

Fett/Lipid

Self Cite

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Olive oil is one of the oldest known vegetable oils, and it is almost unique in that it can be consumed without any refining treatment. One of its most important quality problems is oxidative rancidity due to the oxygenation of polyenoic fatty acids and formation of compounds that derive from these fatty acid hydroperoxides. Beside autoxidation, lipoxygenases (LOXs) were suggested to be involved in this process. Here we show, that approximately 1.6% of all linoleic acid (LA) molecules within olive oil samples had been converted into LOX‐derived (13S,9Z,11E)‐13‐hydroperoxy‐9,11‐octadecadienoic acid (13‐HPODE) as determined by 1H NMR‐ and HPLC analysis. LOX activity tests indicated the occurrence of an active 13‐LOX exhibiting a pH optimum between pH 5.5 and 6.0. Furthermore, this enzyme preferentially metabolized free fatty acids. In order to elucidate the origin of this LOX, we analyzed olive endosperms for LOX forms. Chromatography of total protein extracts of the tissue showed LOX activity almost exclusively associated with a high molecular mass fraction. Light microscopic inspection, as well as the calculated phosphate, neutral lipid, and protein content of this fraction, suggested that this fraction may contain oil bodies and that LOX activity was associated with their membrane. This LOX activity had a pH optimum of 6.0. Activity assays at various temperatures indicated a significant catalytic efficiency of the enzyme up to 55°C. HPLC analysis of LA oxygenation products within the lipid fraction and of activity tests of isolated oil bodies showed that the LOX present in mature olive endosperm oil bodies was, as the enzyme from olive oil, a linoleate 13‐LOX preferentially active on free LA. We suggest, that this oil body LOX from olive endosperm, is the one detected originally in olive oil and may survive at least in part olive oil production.

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The Effect of Kilning on the Capability of Malt to Oxidise Lipids

Kaukovirta-Norja¹,

Laakso²,

Reinikainen³

et al. 1998

Journal of the Institute of Brewing

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The influence of kilning on the ability off malt to oxidise lipids was studied. Barley was malted with a standard programme and subsequently dried with varying kilning procedures. The capability of samples taken during kilning to oxidise lipids was determined by the lipoxygenase (LOX) reaction, i.e. by measuring O2 consumption in an aqueous suspension of samples upon addition of excess amounts of exogenous linoleic acid. Various kilning programmes from isothermal low-temperature kilnings to kilnings with varying temperature profiles induced a two-to threefold increase in the rate of the LOX reaction in the samples taken during the first two to six hours of kilning. However, when lipid changes in the intact kernels were measured, oxidation of the endogenous malt lipids was very limited during the first half of kilning. Furthermore, the rate of the LOX reaction decreased in samples taken during the latter part of kilning, the rate of decrease depending on the kilning programme and especially the final curing temperatures. These results indicate that a possible risk of a marked ability to oxidise lipids remains at moderate kilning temperatures. In conclusion, kilning induces a significant capability to oxidise lipids but does not affect the fatty acid composition of whole kernels. However, in aqueous suspensions of ground malt the oxidative instability created might lead to oxidation of lipids.

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Lipoxygenase‐2 Oxygenates Storage Lipids in Embryos of Germinating Barley

Cited by 48 publications

References 25 publications

Regio- and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2

Regio- and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2

Characterization of a 13-lipoxygenase from virgin olive oil and oil bodies of olive endosperms

The Effect of Kilning on the Capability of Malt to Oxidise Lipids

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