Department of Biochemistry, North Dakota State University, Fargo, North Dakota 58102.
Plant Physiol. 1976 May;57(5):780-8. doi: 10.1104/pp.57.5.780.
Lipoxygenase (EC 1.13.1.13) was found in seedlings of Citrullus lanatus (Thunb.) Matsum. and Nakai (watermelon). The enzyme has pH optima of 4.4 and 5.5 and is inhibited by 0.2 mM nordihydroguaiaretic acid. It is present in two functional units with estimated molecular weights of 120,000 and 240,000, respectively.A new enzyme, tentatively termed hydroperoxide lyase, has been partially purified from watermelon seedlings. The enzyme, located principally in the region of the hypocotyl-root junction, catalyzes the conversion of 13-l-hydroperoxy-cis-9-trans-11-octadecadienoic acid to 12-oxo-trans-10-dodecenoic acid and hexanal. The hydroperoxide lyase enzyme from watermelon has a molecular weight in excess of 250,000, a pH optimum in the range of 6 to 6.5, and is inhibited by p-chloromercuribenzoic acid. Its presence has also been demonstrated in other cucurbits.The maximum activity of both enzymes occurs on the 6th day of germination. The identification of the products of the hydroperoxide lyase reaction suggests that lipoxygenase and hydroperoxide lyase may be involved in the conversion of certain polyunsaturated fatty acids to traumatic acid (trans-2-dodecenedioic acid).
脂氧合酶（EC1.13.1.13）在西瓜（Citrullus lanatus（Thunb.）Matsum.和 Nakai）幼苗中被发现。该酶的最适 pH 值分别为 4.4 和 5.5，并被 0.2mM 去甲二氢愈创木酸抑制。它存在于两个功能单元中，分子量分别估计为 120000 和 240000。
一种新的酶，暂定名为过氧化物裂解酶，已从西瓜幼苗中部分纯化。该酶主要位于下胚轴-根连接区，催化 13-l-过氧-cis-9-trans-11-十八碳二烯酸转化为 12-氧-trans-10-十二烯酸和己醛。西瓜过氧化物裂解酶的分子量超过 250000，最适 pH 值在 6 到 6.5 之间，被对氯汞苯甲酸抑制。它也存在于其他葫芦科植物中。
两种酶的最大活性都出现在发芽的第 6 天。过氧化物裂解酶反应产物的鉴定表明，脂氧合酶和过氧化物裂解酶可能参与某些多不饱和脂肪酸向创伤酸（反式-2-十二烯二酸）的转化。
