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The transport and metabolism of urea in Chara australis: III. Two specific transport systems

Journal Article


Abstract


  • Reciprocal competitive inhibition studies were used to show that N-methyl-urea (NMU), acetamide and urea all compete for binding to a common transport system, designated system I and that this system is one of two specific mechanisms transporting urea in Chara. System I binds urea with a Km of about 0-3 mmol m-3 and is strongly influenced by metabolic controls. System I is active and electrogenic and may be energized by the coupling of urea uptake to an influx of protons. This is the first report of an electrogenic urea transport system in an alga. The second specific mechanism for urea transport, designated system II, binds urea with a relatively low affinity (Km c. 7-0 mmol m-3) and does not transport NMU to a significant extent. System II is less subject to metabolic control than system I and, though it may be active, is not electrogenic. © 1988 Oxford University Press.

Publication Date


  • 1988

Citation


  • Wilson, M. R., O'donohue, S. I., & Walker, N. A. (1988). The transport and metabolism of urea in Chara australis: III. Two specific transport systems. Journal of Experimental Botany, 39(6), 763-774. doi:10.1093/jxb/39.6.763

Scopus Eid


  • 2-s2.0-0001510187

Start Page


  • 763

End Page


  • 774

Volume


  • 39

Issue


  • 6

Abstract


  • Reciprocal competitive inhibition studies were used to show that N-methyl-urea (NMU), acetamide and urea all compete for binding to a common transport system, designated system I and that this system is one of two specific mechanisms transporting urea in Chara. System I binds urea with a Km of about 0-3 mmol m-3 and is strongly influenced by metabolic controls. System I is active and electrogenic and may be energized by the coupling of urea uptake to an influx of protons. This is the first report of an electrogenic urea transport system in an alga. The second specific mechanism for urea transport, designated system II, binds urea with a relatively low affinity (Km c. 7-0 mmol m-3) and does not transport NMU to a significant extent. System II is less subject to metabolic control than system I and, though it may be active, is not electrogenic. © 1988 Oxford University Press.

Publication Date


  • 1988

Citation


  • Wilson, M. R., O'donohue, S. I., & Walker, N. A. (1988). The transport and metabolism of urea in Chara australis: III. Two specific transport systems. Journal of Experimental Botany, 39(6), 763-774. doi:10.1093/jxb/39.6.763

Scopus Eid


  • 2-s2.0-0001510187

Start Page


  • 763

End Page


  • 774

Volume


  • 39

Issue


  • 6