Journal Article

Two Tropinone Reductases, That Catalyze Opposite Stereospecific Reductions in Tropane Alkaloid Biosynthesis, Are Localized in Plant Root with Different Cell-Specific Patterns

Keiji Nakajima and Takashi Hashimoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 11, pages 1099-1107
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029494
Two Tropinone Reductases, That Catalyze Opposite Stereospecific Reductions in Tropane Alkaloid Biosynthesis, Are Localized in Plant Root with Different Cell-Specific Patterns

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In the plant species that produce tropane alkaloids, two tropinone reductases (TRs) catalyze the stereospecific reductions of the 3-carbonyl group of tropinone. This reduction is a key branch point that determines the metabolite flow into the separate alkaloid groups, each with different stereospecific configurations. In this study, a specific antibody was prepared for each of the TRs by immunizing mice with recombinant TR protein and subsequent immuno-affinity purification of the antiserum. Immunoblot analyses revealed that accumulation of both TRs was highest in the lateral roots of Hyoscyamus niger through-out its development. In cultured roots, TR proteins were accumulated in a basal region but not in root apex. These patterns were similar to that of hyoscyamine 6β-hydroxylase (H6H), an enzyme that catalyzes a downstream step in the same biosynthetic pathway. However, an immuno-histochemical analysis revealed that the two TRs and H6H were accumulated with different cell-specific patterns in the cultured root, suggesting transportation of the alkaloid intermediate(s) across the different cell layers.

Keywords: Hyoscyamus niger; Immunohistochemistry; Tropane alkaloids; Tropinone reductases (EC 1.1.1.206 and EC 1.1.1.236); Stereospecificity

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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