小麦叶片顺乌头酸酶对NO和H2 O2 的敏感性

外源一氧化氮（nitric oxide,NO)供体硝普钠（sodium nitroprusside,SNP)和过氧化氢（hydrogen peroxide,H2O2)处理抑制小麦（Triticu aestivum L.)叶片顺乌头酸酶活性，抑制呈明显的浓度及时间效应；同时外源NO衍生代谢物过氧亚硝酸阴离子（peroxynitrite,ONOO^-)的供体3－morpholinosydnonimine hydrochlloride(SIN-1)和水杨酸（salicylic acid,SA)对酶活性也具有抑制作用，而且小麦叶片线粒体顺乌头酸酶对H2O2和SIN－1更敏感。分别以SNP与过氧化氢酶（catalase,CAT)专一性抑制剂氨基三唑（3－amino-1,2,4-triazole,3-AT)处理离体小麦叶片，发现在其内源H2O2含量上升的同时，顺乌头酸酶活性均呈浓度与时间依赖性下降趋势。表明NO除直接抑制顺乌头酸酶活性外，还可能经H2O2介导间接对顺乌头酸酶产生抑制作用。

Sensitivity of Wheat Leaf Aconitase to Nitric Oxide and Hydrogen Peroxide

Exogenous nitric oxide (NO) donor, sodium nitroprusside (SNP) and hydrogen peroxide (H 2O 2), dramatically inhibited the activities of aconitase from wheat ( Triticum aestivum L.) leaves. The results indicated that this inhibition was in significantly dose and time dependent manners (Figs.1,2). In addition, exogenous peroxynitrite (ONOO - ) derived from its donor 3 morpholinosydnonimine hydrochloride (SIN 1) and salicylic acid (SA) also inactivated aconitase from wheat leaves (Table 1, Fig.2). Among these substances, H 2O 2 and SIN 1 showed the greatest inhibition to mitochondria aconitase. When treated with SNP and 3 amino 1,2,4 triazole (3 AT), a specific inhibitor of catalase (CAT), the levels of endogenous H 2O 2 in detached wheat leaves increased (Fig.3B, Fig.4) while aconitase activities decreased, which depended on dose (Fig.3A) and time dependent (Fig.4) manners. The above results showed that in addition to the direct inactivation of aconitase activity by NO, NO could possibly inhibit its activity indirectly through the action of H 2O 2 formed by induction by NO.