产甲烷条件下吲哚类有机物的降解途径

DEGRADATION PATHWAYS AND MECHANISMS OF SUBSTITUTED INDOLES UNDER METHANOGENIC CONDITION

产甲烷条件下从废水污泥中驯化的细菌对吲哚的降解包括两步羰基化反应 ,生成中间产物氧化吲哚和靛红 .本文研究了产甲烷条件下细菌降解吲哚类有机物的能力 .在所研究的吲哚类化合物中 ,细菌在产甲烷条件下可以降解 3 甲基吲哚和 3 吲哚醋酸酯 .氧化吲哚 ,3 甲基氧化吲哚和羰基吲哚分别为吲哚、3 甲基吲哚和 3 吲哚醋酸酯的代谢产物 .产甲烷条件下细菌可降解氧化吲哚并生成中间产物靛红 ,这证明了在吲哚降解过程中 ,吲哚吡咯环在2、3位碳间断裂之前连续进行了两步羰基化 .吲哚 1位和 2位上甲基的存在 ,抑制了羰基化反应 .3 甲基吲哚可在 2位上羰基化 ,但不能在 3位上羰基化 ,所以不能通过氧化吲哚———靛红途径进行代谢 .3 吲哚醋酸酯的脱乙酰产物———羰基吲哚也不能在 2位上羰基化 ,所以不能被进一步代谢 .当 3位上有H原子或供电子基团时 ,羰基化可在 2位上进行 ,但 3位上的吸电子取代基团会抑制羰基化 .表 1图 4参 2

Degradation of indole by an indole degrading methanogenic consortium enriched from sewage sludge proceeded through a two step hydroxylation pathway yielding oxindole and isatin. The ability of this consortium to hydroxylate and subsequently degrade substituted indoles was investigated. Of the substituted indoles tested, the consortium was able to transform or degrade 3 methylindole and 3 indolyl acetate. Oxindole, 3 methyloxindole, and indoxyl were identified as degradation metabolites of indole, 3 methylindole, and 3 indolyl acetate, respectively. Isatin (indole 2, 3 dione) was produced as an intermediate when the consortium was amended with oxindole, which provided the evidence that degradation of indole proceeded through successive hydroxylation of the 2 and 3 positions prior to ring cleavage between the C 2 and C 3 atoms on the pyrrole ring of indole. The presence of a methyl group ( CH 3 ) at either the 1 or 2 position of indole inhibited the initial hydroxylation reaction. The substituted indole, 3 methylindole, was hydroxylated at the 2 position but not at the 3 position and could not be further metabolized through the oxindole isatin pathway. Indoxyl (indole 3 one), the deacetylated product of 3 indolyl acetate, was not hydroxylated at the 2 position and thus was not further metabolized by the consortium. When an H atom or electron donating group (i.e., CH 3 ) was present at the 3 position, hydroxylation proceeded at the 2 position, but the presence of electron withdrawing substituent groups (i.e., OH or COOH) at the 3 position inhibited hydroxylation. Tab 1, Fig 4, Ref 25