Dioxygenases Catalyze O-Demethylation and O,O-Demethylenation with Widespread Roles in Benzylisoquinoline Alkaloid Metabolism in Opium Poppy
Dioxygenases Catalyze O-Demethylation and O,O-Demethylenation with Widespread Roles in Benzylisoquinoline Alkaloid Metabolism in Opium Poppy
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DOI：
10.1074/jbc.m113.488585
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发表时间：
2013-10-04
影响因子：
4.8
通讯作者：
Facchini, Peter J.
中科院分区：
文献类型：
--
作者：
Farrow, Scott C.;Facchini, Peter J.
在罂粟中，吗啡生物合成的倒数第二步和最后一步由2-酮戊二酸/Fe（II）依赖性双加氧酶、蒂巴因6-O-脱甲基酶（T6 ODM）和可待因O-脱甲基酶（CODM）催化。对CODM和T6 ODM的生化功能的进一步研究揭示了这些酶在原阿片碱、苯并[c]菲啶和罗丹生物碱代谢中的广泛和意想不到的作用。当用广泛的苄基异喹啉生物碱、CODM、T6 ODM和功能上未分配的paramycin DIOX 2（重命名为原阿片碱O-脱烷基酶）进行测定时，显示出新颖且有效的脱烷基化活性，包括区域特异性和底物特异性O-脱甲基化和O，O-脱亚甲基化。催化O，O-脱亚甲基化的酶，其裂解亚甲二氧基桥留下两个羟基，以前没有在植物中报道。在哺乳动物中，血红素依赖性细胞色素P450催化取代安非他明上亚甲二氧基桥的类似裂解。通过CODM和原阿片碱O-脱烷基酶进行O，O-脱亚甲基化的优选底物是原阿片碱生物碱，其在苯并[c]菲啶和rhoeadine衍生物的生物合成中充当中间体。用于抑制CODM和/或T6 ODM转录物丰度的病毒诱导的基因沉默表明这些酶在原阿片碱生物碱代谢中的直接生理作用，并且它们揭示了它们间接参与罂粟中抗微生物的苯并[c]菲啶血根碱和某些rhoeadine生物碱的形成。
In opium poppy, the antepenultimate and final steps in morphine biosynthesis are catalyzed by the 2-oxoglutarate/Fe(II)-dependent dioxygenases, thebaine 6-O-demethylase (T6ODM) and codeine O-demethylase (CODM). Further investigation into the biochemical functions of CODM and T6ODM revealed extensive and unexpected roles for such enzymes in the metabolism of protopine, benzo[c]phenanthridine, and rhoeadine alkaloids. When assayed with a wide range of benzylisoquinoline alkaloids, CODM, T6ODM, and the functionally unassigned paralog DIOX2, renamed protopine O-dealkylase, showed novel and efficient dealkylation activities, including regio- and substrate-specific O-demethylation and O,O-demethylenation. Enzymes catalyzing O,O-demethylenation, which cleave a methylenedioxy bridge leaving two hydroxyl groups, have previously not been reported in plants. Similar cleavage of methylenedioxy bridges on substituted amphetamines is catalyzed by heme-dependent cytochromes P450 in mammals. Preferred substrates for O,O-demethylenation by CODM and protopine O-dealkylase were protopine alkaloids that serve as intermediates in the biosynthesis of benzo[c]phenanthridine and rhoeadine derivatives. Virus-induced gene silencing used to suppress the abundance of CODM and/or T6ODM transcripts indicated a direct physiological role for these enzymes in the metabolism of protopine alkaloids, and they revealed their indirect involvement in the formation of the antimicrobial benzo[c]phenanthridine sanguinarine and certain rhoeadine alkaloids in opium poppy.