Gu J D, Berry D F
Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Appl Environ Microbiol. 1991 Sep;57(9):2622-7. doi: 10.1128/aem.57.9.2622-2627.1991.
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 metabolites of indole, 3-methylindole, and 3-indolyl acetate degradation, respectively. Isatin (indole-2,3-dione) was produced as an intermediate when the consortium was amended with oxindole, providing 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 (-CH3) at either the 1- or 2-position of indole inhibited the initial hydroxylation reaction. The substituted indole, 3-methylindole, was hydroxylated in the 2-position but not in 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 in the 2-position and thus was not further metabolized by the consortium. When an H atom or electron-donating group (i.e., -CH3) 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.
从污水污泥中富集得到的一个降解吲哚的产甲烷菌联合体对吲哚的降解是通过两步羟基化途径进行的，生成了氧化吲哚和异吲哚酮。对该联合体羟基化并随后降解取代吲哚的能力进行了研究。在所测试的取代吲哚中，该联合体能够转化或降解3-甲基吲哚和3-吲哚乙酸酯。氧化吲哚、3-甲基氧化吲哚和吲哚酚分别被鉴定为吲哚、3-甲基吲哚和3-吲哚乙酸酯降解的代谢产物。当向该联合体中添加氧化吲哚时，会产生异吲哚酮（吲哚-2,3-二酮）作为中间产物，这证明吲哚的降解是在吲哚吡咯环的C-2和C-3原子之间发生环裂解之前，通过2-位和3-位的连续羟基化进行的。吲哚的1-位或2-位存在甲基（-CH3）会抑制初始羟基化反应。取代吲哚3-甲基吲哚在2-位发生了羟基化，但在3-位没有，并且不能通过氧化吲哚-异吲哚酮途径进一步代谢。吲哚酚（吲哚-3-酮）是3-吲哚乙酸酯的脱乙酰产物，在2-位没有发生羟基化，因此不能被该联合体进一步代谢。当3-位存在氢原子或供电子基团（即-CH3）时，羟基化在2-位进行，但3-位存在吸电子取代基（即-OH或-COOH）会抑制羟基化。
