Hyoscyamine, a member of the class of compounds known as tropane alkaloids (TAs), is clinically used as an anticholinergic drug. Previous research has predicted that hyoscyamine is produced via the reduction of hyoscyamine aldehyde. In this study, we identified a root-expressed gene from Atropa belladonna, named AbHDH, which encodes a hyoscyamine dehydrogenase involved in the formation of hyoscyamine. Enzymatic assays indicated that AbHDH was able to not only reduce hyoscyamine aldehyde to produce hyoscyamine but also oxidize hyoscyamine to form hyoscyamine aldehyde under different conditions. To elucidate its catalytic mechanism, the crystal structure of AbHDH at a 2.4-Å resolution was also determined. Overexpression of AbHDH significantly enhanced the biosynthesis of hyoscyamine and the production of anisodamine and scopolamine in root cultures of A. belladonna. However, suppression of AbHDH using RNAi technology did not reduce the production of hyoscyamine, anisodamine, or scopolamine, though it did increase the accumulation of hyoscyamine aldehyde. In summary, this study provided timely biochemical and metabolic insights into hyoscyamine dehydrogenase, pointing to an alternative, promising way to produce pharmaceutical TAs via metabolic engineering in planta.

中文翻译：

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硫胺素脱氢酶的生化和代谢见解。

菱胺是被称为托烷生物碱（TAs）的一类化合物，在临床上被用作抗胆碱能药物。先前的研究预测，通过减少丝胺醛可产生丝胺。在这项研究中，我们从颠茄颠茄中鉴定出了一个根表达基因，命名为AbHDH，该基因编码参与hysocyamine形成的hysocyamine脱氢酶。酶法测定结果表明，AbHDH不仅能够还原糖胺醛以生成糖胺，而且还可以在不同条件下氧化糖胺以形成糖胺醛。为了阐明其催化机理，还确定了分辨率为2.4Å的AbHDH的晶体结构。AbHDH的过表达显着增强了颠茄根培养中硫胺的生物合成以及山d碱和东pol碱的产生。但是，使用RNAi技术抑制AbHDH并不会减少丝胺，山，碱或东pol碱的产生，尽管确实会增加丝胺醛的积累。总而言之，这项研究提供了对羟乙胺脱氢酶的及时生化和代谢方面的见解，指出了另一种通过植物中的代谢工程生产药物TA的有前途的方法。