title: Biosynthesis of steroidal alkaloids in Solanaceae plants: involvement of an aldehyde intermediate during C-26 amination.
abstract: The C-26 amino group of steroidal alkaloids, such as tomatine, is introduced during an early step of their biosynthesis from cholesterol. In the present study, the mechanism of C-26 amination was reinvestigated by administering stable isotope labeled compounds, such as (26,26,26,27,27,27-(2)H6)cholesterol during biosynthesis of tomatine, solanine and solasonine. The chemical compositions of tomatine and solanine so obtained were analyzed by LC-MS after administering the d6-cholesterol to a tomato seedling and a potato shoot, respectively. The resulting spectra indicated that two deuterium atoms were eliminated from C-26 of cholesterol during biosynthesis. Furthermore, administration of (6-(13)C(2)H3)mevalonate in combination with lovastatin to an eggplant seedling, followed by GC-MS analysis of solasodine after TMS derivatization established that two deuterium atoms were eliminated from C-26 of cholesterol during solasonine biosynthesis. These findings are in contrast to an earlier observation that one hydrogen atom was lost from C-26 during tomatidine biosynthesis, and suggest that C-26 nitrogen atom addition involves an aldehyde intermediate. Thus, it is proposed that the C-26 amination reaction that occurs during steroidal alkaloid biosynthesis proceeds by way of a transamination mechanism.
authors.affiliation: Department of Chemistry and Materials Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan. ohyama.k.aa@m.titech.ac.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ohyama
authors.forename: Akiko
authors.initials: A
authors.lastname: Okawa
authors.forename: Yuka
authors.initials: Y
authors.lastname: Moriuchi
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Fujimoto
mesh_terms: D000447:Aldehydes / Q000378:metabolism*; D000470:Alkaloids / Q000096:biosynthesis* / Q000737:chemistry*; D000586:Amination; D019657:Solanaceae / Q000378:metabolism*; D013256:Steroids / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D000470:Alkaloids; D013256:Steroids