Isolation and Action Mechanism of Oxidation Enzyme of Unsaturated Fatty Acids produced in Rice Plants suffered from Stress.

1. 稻瘟病菌侵染与水稻脂氧合酶活性的关系虽然人们早就认识到水稻植株对稻瘟病菌的易感和抗性取决于稻瘟病菌的品种，但其生理机制至今仍不清楚。用特定菌种侵染Sasanishiki、Homarenishiki等6种水稻植株，使其产生相应的感、抗性病变，测定其脂氧合酶活性。结果表明，在感染后7 d，所有易感病灶的脂氧合酶活性均显著升高。另一方面，在每例抗性病变感染后3天观察到活性最大值。这些发现清楚地表明，侵染水稻的小褐变（r型）和大褐变（s型）的形成机制与脂氧合酶的活性密切相关，脂氧合酶将不饱和脂肪酸转化为细胞毒性的氢过氧化物衍生物。几种不饱和脂肪酸的脂加氧酶氧化研究脂加氧酶对几种不饱和脂肪酸的氧化作用：亚麻酸、< α - >-亚油酸和< α - >-亚油酸、花生四烯酸、二十碳五烯酸和二十二碳六烯酸。结果表明，脂合酶的氧化过程具有区域和立体特异性，生成了相应的过氢不饱和脂肪酸。这些酸是研究不饱和脂肪酸在生物体中的作用的通用化合物。LTB_4型化合物的结构与合成通过合成研究，证实了从侵染水稻植株中分离得到的一种高氧脂肪酸的结构为9,16-二羟基-十八烷-10,12,14-三烯酸。

1. RELATIONSHIP BETWEEN INFECTION AND LIPOXYGENASE ACTIVITY IN RICE PLANTSAlthough it has been recognized for a long time that the rice plants become susceptible and resistant depending on the race of the rice blast fungus, its physiological mechanism has remained unsolved until now. After six kinds of rice plants such as Sasanishiki, Homarenishiki and so on were infected with specific race of the fungus to make the corresponding susceptible and resistant lesions, the lipoxygenase activity were assayed. It was revealed that the lipoxygenase activity in all the susceptible lesions increased greatly at 7 days after infection. On the other hands, the activity maxima were observed at 3 days after infection in each case of resistant lesions. These findings demonstrate clearly that formation mechanism of small brown (R-type) and large (S-type) lesions of the infected rice are closely related with the activity of lipoxygenase by which the unsaturated fatty acid is transformed into cytotoxic hydroperoxy derivatives.2. OXIDATION OF SEVERAL UNSATURATED FATTY ACIDS WITH LIPOXYGENASE FROM RICE PLANTSThe following typical unsaturated fatty acids were submitted to the action of lipoxygenase; linolenic acid, <alpha>_- and <gamma>-linoleic acids, arachidonic acid, eicosapentenoic acid, and docosahexenoic acid, respectively. It was found that the liposygenase oxidation proceeded regio and stereospecifically, offording the corresponding perhydro unsaturated fatty acids. These acids are versatile compounds in studying the role of unsaturated fatty acids in the living bodies.3. STRUCTURE AND SYNTHESIS OF THE LTB_4 TYPE COMPOUNDBy the synthetic study, it was demonstrated that the structure of one of the highly oxygenated fatty acid isolated from the infected rice plant was 9,16-dihydroxy- octadeca-10,12,14-trienoic acid.