Dual Positional and Stereospecificity of Lipoxygenase Isoenzymes from Germinating Barley (Green Malt):  Biotransformation of Free and Esterified Linoleic Acid

Abstract

The lipoxygenase isoenzymes LOX1 and LOX2 from green malt were separated by isoelectric focusing, and their catalytic properties regarding complex lipids as substrates were characterized. The regio- and stereoisomers of hydroperoxy octadecadienoates (HPODE) resulting from LOX1 and LOX2 enzymatic transformations of linoleic acid, methyl linoleate, linoleic acid glycerol esters monolinolein, dilinolein, and trilinolein, and 1-palmitoyl-2-linoleoyl-glycero-3-phosphocholine (PamLinGroPCho) were determined. In addition, biotransformations of polar and nonpolar lipids extracted from malt were performed with LOX1 and LOX2. The results show that LOX2 catalyzes the oxidation of esterified fatty acids at a higher rate and is more regioselective than LOX1. The dual position specificity of LOX2 (9-HPODE:13-HPODE) with trilinolein as the substrate (6:94) was higher than the resultant ratio (13:87) when free linoleic acid was transformed. A high (S)-enantiomeric excess of 13-HPODE was analyzed with all esterified substrates confirming the formation of 13-HPODE through the LOX2 enzyme; however, 9-HPODE detected after LOX2 biotransformations showed (R)-enantiomeric excesses. PamLinGroPCho was oxygenated by LOX1 with the highest regio- and stereoselectivities among the applied substrates.

A Review on the Source of Lipids and Their Interactions during Beer Fermentation that Affect Beer Quality

“…A positive correlation between the specific density of beer wort samples and their fatty acid content was reported [18,28]. Moreover, the composition of fatty acids in the wort was explained by considering the variety of malt used and the potential of lipolytic activity, which involves the action of lipase, lipoxygenase and hydroperoxy fatty acid catalysing enzymes, during wort production [18,28,[39][40][41].…”

Jasmonate Biosynthesis, Perception and Function in Plant Development and Stress Responses

“…LOXs adding O2 to C-9 or C-13 of the hydrocarbon backbone of LA are designated as 9-LOX or 13-LOX (Feussner and Wasternack, 2002). However, in plants some LOXs have dual positional specificity to C-9 and C-13 of LA and produce both 9-and 13-hydroperoxides of linoleic acid (Hughes et al 2001, Garbe et al 2006. Plants LOXs were found in several subcellular compartments including chloroplast, vacuole and cytosol.…”

Biochemical properties of lipoxygenase from opium poppy chloroplasts

“…However, LOX of some plant species were found to have a dual positional specificity and produce both 9-and 13-hydroperoxides of linoleic acid (Hughes et al 2001, Kim et al 2002, Garbe et al 2006. The most recent classification of plant LOX is based on the relationship in the DNA coding sequences and amino acid sequences respectively.…”