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Regio– and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2
Author(s) -
Almeida Roberto Barbosa,
Garbe LeifAlexander,
Nagel Renate,
Wackerbauer Karl,
Tressl Roland
Publication year - 2005
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.2005.tb00682.x
Subject(s) - linoleic acid , isoelectric focusing , chemistry , biochemistry , enzyme , biology , fatty acid
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 stereo‐selectivity 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.