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Nitrogen recycling during phenylpropanoid metabolism in sweet potato tubersIn the first step of the phenylpropanoid metabolic pathway, L-phenylalanine (L-Phe) is deaminated to form E-cinnamate, in a conversion catalyzed by phenylalanine ammonia-lyase (PAL; EC 4.3.1.5). The metabolic fate of the ammonium ion (NH4+) produced in this reaction was investigated in sweet potato (Ipomoea batatas) tuber discs. [15N]-Labeled substrates including L-Phe, in the presence or absence of specific enzyme inhibitors, were administered to sweet potato discs in light under aseptic conditions. 15N-Nuclear magnetic resonance spectroscopic analyses revealed that the 15NH4+ liberated during the PAL reaction is first incorporated into the amide nitrogen of L-glutamine (L-Gln) and then into L-glutamate (L-Glu). These results extend our previous observations in pine and potato that PAL-generated NH4+ is assimilated by the glutamine synthetase (GS; EC 6.3.1.2)/glutamate synthase (GOGAT; EC 1.4.1.13) pathway, with the NH4+ so formed ultimately being recycled back to L-Phe via L-Glu as aminoreceptor and donor.
Document ID
20040088793
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Singh, S.
(University of British Columbia Vancouver, Canada)
Lewis, N. G.
Towers, G. H.
Date Acquired
August 21, 2013
Publication Date
October 1, 1998
Publication Information
Publication: Journal of plant physiology
Volume: 153
Issue: 4-Mar
ISSN: 0176-1617
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG10-0164
CONTRACT_GRANT: DE-FG06-91-ER20022
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Plant Biology

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