Rapid Methods for Lipoxygenase Assay in Sweet Corn

Abstract

Potential methods for rapid assay of sweet corn lipoxygenase (LPO) were evaluated and compared by visual inspection. Both model system (partially purified) and vegetable (LPO extract) system studies were carried out. Model system studies indicated that LPO had maximum activity at pH 6.0 and 2.0 mM linoleic acid. Methylene blue bleaching (MBB), carotene bleaching (CB), and potassium iodide-starch (KI-S) methods were evaluated both spectrophotometrically and visually. Both MBB and KI-S methods were effective for the model system. For the vegetable LPO extract systems (sweet corn and green beans), the MBB method indicated positive results for both, the CB method was not effective for either, and the KI-S method was very effective for green beans but not for sweet corn.

Lipoxygenase activity in walnuts and almonds

“…2). LOX in plants exhibit optimum activity in the range of pH 5.5-7.5 (Romero & Barrett, 1997). Fig.…”

Changes in lipoxygenase properties and activity related to postgerminative growth and senescence in oat (Avena sativa L cv. Victory 1 )

“…However, contradictory results have been reported with other species. For example, the optimum LOX activity is at pH 6.0 for sweet corn (Romero and Barrett, 1997), pH 5.5 for potato tubers (Mu[liez et al, 1987), and pH 7.5 for purified LOX from barley grains (Yabuuchi and Amaha, 1975). In senescing carnation petals, soluble LOX has an optimum pH range of 4.9 to 5.8, with microcosma[ LOX exhibiting its maximum activity at pH 6.1 (Rouet-Mayer et al, 1992).…”

“…Using a DEAE-Trisacryl column, Mulliez et al (1987) have demonstrated that potato tubers contain at least three LOX isoenzymes. Romero and Barrett (1997) have found that LOX activity from sweet corn is highest at 2.00 mM linoleic acid, at both pH 6.6 and 7.0. Furthermore, Lagocki et al (1976) has used kinetic analysis of soybean LOX on [inoleic acid to propose that, because LOX is a dimeric enzyme, there are two equivalent sites for activation and catalysis.…”

“…A 100-~L aliquot of Tween 20 and the linoleic acid was added to a 1.0-mL cuvette containing 1 mL of 50 mM mixing buffer --Tris-HCI, sodium phosphate, and citric acid (pH 4.5). Then, 10 pL of the extract solution was added to the cuvette to assay for LOX activity (Romero and Barrett, 1997). Changes in absorbance at 234 nm (25~ were monitored; the reaction was linear for at least 10 rain.…”

Lipoxygenase in senescing cut leaves of Zantedeschia aethiopica Spr. and Hosta ‘Undulata erromena’ treated with GA3 or BA

“…The ac tiv ity of lipoxygenase (LOX; EC 1.13.11.12) was de ter mined spec tro pho to met ri cally at 660 nm by Meth y lene Blue Bleach ing Method (Suda et al 1995, mod i fied by Romero and Barrett 1997). Re sults are given in ar bi trary units (changes in absorbance dur ing 1 min ute of re ac tion) per gram of ac e tone pow der.…”