Doderer A, Kokkelink I, van der Veen S, Valk B E, Schram A W, Douma A C
Heineken Technisch Beheer, Zoeterwoude, Netherlands.
Biochim Biophys Acta. 1992 Mar 27;1120(1):97-104. doi: 10.1016/0167-4838(92)90429-h.
Two lipoxygenase isoenzymes (linoleate: oxygen oxidoreductase, EC 1.13.11.12) present in the embryo of germinating barley seed have been purified to homogeneity and characterized. Both isoenzymes are monomeric proteins with a molecular mass of approx. 90 kDa and crossreact on Western blots with antibodies raised against pea lipoxygenase. They have an apparent Km of approx. 16 microM for linoleic acid. The isoenzymes differ in the product formed upon incubation with linoleic acid. One of the isoenzymes (lipoxygenase 1) solely forms the 9-HPOD as a product whereas the 13-HPOD is the major product formed by the other isoenzyme (lipoxygenase 2). Lipoxygenase 1 shows a pH-optimum of 6.5, is active in a broad pH range and has an isoelectric point of 5.2-5.3. Lipoxygenase 2 has the same pH optimum, but is active in a narrow pH range and has a significantly higher pI, namely 6.8-6.9. The occurrence of two isoenzymes was confirmed by peptide analysis of the proteins. Amino acid sequence data obtained from proteolytic fragments of lipoxygenase 1 show up to 50% identity with other plant lipoxygenases.
在发芽大麦种子胚中存在的两种脂氧合酶同工酶（亚油酸：氧氧化还原酶，EC 1.13.11.12）已被纯化至同质并进行了特性鉴定。两种同工酶均为单体蛋白，分子量约为90 kDa，在蛋白质印迹法中与针对豌豆脂氧合酶产生的抗体发生交叉反应。它们对亚油酸的表观Km约为16 μM。这两种同工酶在与亚油酸孵育时形成的产物有所不同。其中一种同工酶（脂氧合酶1）仅形成9 - 氢过氧十八碳二烯酸作为产物，而13 - 氢过氧十八碳二烯酸是另一种同工酶（脂氧合酶2）形成的主要产物。脂氧合酶1的最适pH为6.5，在较宽的pH范围内有活性，等电点为5.2 - 5.3。脂氧合酶2具有相同的最适pH，但在较窄的pH范围内有活性，且等电点显著更高，即6.8 - 6.9。通过对蛋白质的肽分析证实了两种同工酶的存在。从脂氧合酶1的蛋白水解片段获得的氨基酸序列数据显示与其他植物脂氧合酶有高达50%的同一性。
