Submitted to: Journal of Cereal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/2/1996
Publication Date: N/A
Citation: Interpretive Summary: Lipoxygenase is an enzyme in barley that causes beer staling. In this study, we developed a rapid test to determine the amounts of lipoxygenase present in germinating barley and evaluated the lipoxygenase levels of eight different barley cultivars. The developed test takes only 25 minutes, and more that 90% of the lipoxygenase enzyme activity was recovered. The levels of lipoxygenase varied between barley cultivars, suggesting that we can breed barley with lower levels. The rapid test will allow us to find the location of genes that regulate lipoxygenase activity.
Technical Abstract: Lipoxygenase (LOX) initiates the peroxidation of unsaturated fatty acids in barley, and may be the determining enzyme in the beer staling process. The objectives of this study were to establish a rapid separation procedure for LOX isoenzymes in germinating barley, and to examine the genotypic variability for LOX isoenzyme activity among eight six-rowed barley cultivars. Two LOX activities in a crude extract of germinated barley were resolved readily by fast protein liquid chromatography (FPLC) on a Mono Q HR 5/5 anion-exchange column. Separation was achieved in 25 minutes, and recovery of activity was consistently greater than 90%. The two LOX activities were identified as LOX-1 and LOX-2 by isoelectric focusing, and by comparison to the chromatographic properties of purified LOX-1 and LOX-2. The two isoenzymes and total LOX varied significantly among the cultivars, although the ratio of LOX-1/LOX-2 was fairly constant. Significant variation of LOX activity between cultivars suggests that the LOX activity in malting barley might be reduced through breeding. The established separation procedure may be useful for screening barley lines for LOX-null mutants, and may facilitate mapping genes that affect LOX activity or levels.