Metabolism of some amino acids in relation to the photorespiratory nitrogen cycle of pea leaves |
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Authors: | T C Ta K W Joy |
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Institution: | (1) Department of Biology, Carleton University, K1S 5B6 Ottawa, Ont, Canada;(2) Institute of Biochemistry, Carleton University, K1S 5B6 Ottawa, Ont, Canada |
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Abstract: | 15N-labelled (amino group) asparagine (Asn), glutamate (Glu), alanine (Ala), aspartate (Asp) and serine (Ser) were used to study the metabolic role and the participation of each compound in the photorespiratory N cycle ofPisum sativum L. leaves. Asparagine was utilised as a nitrogen source by either deamidation or transamination, Glu was converted to Gln through NH3 assimilation and was a major amino donor for transamination, and Ala was utilised by transamination to a range of amino acids. Transamination also provided a pathway for Asp utilisation, although Asp was also used as a substrate for Asn synthesis. In the photorespiratory synthesis of glycine (Gly), Ser, Ala, Glu and Asn acted as sources of amino-N, contributing, in the order given, 38, 28, 23, and 7% of the N for glycine synthesis; Asp provided less than 4% of the amino-N in glycine. Calculations based on the incorporation of15N into Gly indicated that about 60% (Ser), 20% (Ala), 12% (Glu) and 11% (Asn) of the N metabolised from each amino acid was utilised in the photorespiratory nitrogen cycle.Abbreviations Ala
alamine
- Asn
asparagine
- Asp
aspartate
- Glu
glutamate
- MOA
methoxylamine
- Ser
serine |
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Keywords: | Amino acid metabolism Glycine synthesis Nitrogen cycle Photorespiratory N cycle Pisum (photorespiratory N cycle) |
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