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首页> 外文期刊>The Biochemical Journal >MECHANISM OF INDOLE-3-ACETIC ACID OXIDATION BY PLANT PEROXIDASES - ANAEROBIC STOPPED-FLOW SPECTROPHOTOMETRIC STUDIES ON HORSERADISH AND TOBACCO PEROXIDASES
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MECHANISM OF INDOLE-3-ACETIC ACID OXIDATION BY PLANT PEROXIDASES - ANAEROBIC STOPPED-FLOW SPECTROPHOTOMETRIC STUDIES ON HORSERADISH AND TOBACCO PEROXIDASES

机译：植物过氧化物酶对吲哚-3-乙酸的氧化机理-辣根和烟草过氧化物酶的厌氧停止流动光度法研究

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Indole-3-acetic acid (IAA) is a powerful plant growth regulator. The oxidative decarboxylation of IAA by plant peroxidases is thought to be a major degradation reaction involved in controlling the in vivo level of IAA. Horseradish peroxidase isoenzyme C and an anionic tobacco peroxidase isolated from transgenic Nicotiana sylvestris have been used in experiments in vitro designed to determine the mechanism of IAA oxidation. In particular, the initial reduction of ferric to ferrous enzyme, a key step in previously proposed mechanisms, has been investigated by rapid-scan stopped-flow spectrophotometry under strictly anaerobic conditions and at defined oxygen concentrations. The data provide the first evidence for a ternary complex comprising peroxidase, IAA and oxygen that is kinetically competent both at the initiation stage and during the catalytic cycle of IAA oxidation. A general scheme describing the oxidative cycles of both anionic and cationic peroxidases is proposed that includes native ferric enzyme and compound II as kinetically competent intermediates. For anionic peroxidases, addition of hydrogen peroxide switches on the oxidative cycle thereby promoting IAA oxidation. 2-Methyl-IAA is not a substrate of the oxidase reaction, suggesting a specific interaction between plant peroxidases and IAA. [References: 17]
机译：吲哚-3-乙酸（IAA）是一种功能强大的植物生长调节剂。 IAA被植物过氧化物酶氧化脱羧被认为是参与控制IAA体内水平的主要降解反应。从转基因烟草中分离出的辣根过氧化物酶同工酶C和阴离子烟草过氧化物酶已用于体外实验中，以确定IAA的氧化机理。特别是，在严格厌氧条件下和确定的氧气浓度下，通过快速扫描停止流式分光光度法研究了铁还原为亚铁酶的过程，这是先前提出的机制的关键步骤。数据提供了包含过氧化物酶，IAA和氧气的三元复合物的初步证据，该三元复合物在IAA氧化的起始阶段和催化循环过程中均具有动力学能力。提出了描述阴离子和阳离子过氧化物酶的氧化循环的通用方案，其包括天然铁酶和化合物II作为动力学有效的中间体。对于阴离子过氧化物酶，添加过氧化氢会切换氧化循环，从而促进IAA氧化。 2-甲基-IAA不是氧化酶反应的底物，表明植物过氧化物酶和IAA之间存在特异性相互作用。 [参考：17]

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