Nitrogen-15 NMR studies of nitrogen metabolism in Picea glauca buds.
In vivo (15)N nuclear magnetic resonance (NMR) as well as (15)N solid-state magic angle spinning (MAS) NMR spectroscopy were used to investigate nitrogen metabolism in cultured white spruce (Picea glauca) buds. Long-term as well as short-term experiments were carried out involving the use of inhibitors of the nitrogen pathways such as methionine sulfoximine (MSO), azaserine (AZA) and aminooxyacetate (AOA). Both in vivo and solid-state NMR showed that when MSO blocked glutamine synthetase (GS) no NH(4)(+) is incorporated. When glutamate synthase (GOGAT) is blocked by AZA there is some incorporation into glutamine (Gln), but very little into alpha-amino groups (glutamate, Glu). The transamination inhibitor AOA does not affect the metabolism of (15)NH(4)(+) into Gln and Glu, but blocks the production of arginine (Arg), as would be expected. Proline (Pro) and gamma-aminobutyric acid (GABA), which are produced directly from Glu without a transamination step, were not affected. The solid-state NMR experiments showed that protein synthesis occurred. Collectively, our results show that NH(4)(+) can only be assimilated through the GS/GOGAT pathway in P. glauca buds.
Bagh
Kirsten
K
Division of Biochemistry, Department of Biological Sciences, University of Calgary, Calgary, Alta., Canada T2N 1N4.
Hiraoki
Toshifumi
T
Thorpe
Trevor A
TA
Vogel
Hans J
HJ
D000625:Aminooxyacetic Acid / Q000494:pharmacology; D001377:Azaserine / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008717:Methionine Sulfoximine / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism*; D028222:Picea / Q000187:drug effects / Q000378:metabolism*
D000625:Aminooxyacetic Acid; D008717:Methionine Sulfoximine; D001377:Azaserine; D009584:Nitrogen