Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Biochemical characterization, mitochondrial localization, expression, and potential functions for an Arabidopsis γ-aminobutyrate transaminase that utilizes both pyruvate and glyoxylate

Shawn M. Clark, Rosa Di Leo, Preetinder K. Dhanoa, Owen R. Van Cauwenberghe, Robert T. Mullen and Barry J. Shelp
Journal of Experimental Botany
Vol. 60, No. 6 (2009), pp. 1743-1757
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/24037789
Page Count: 15
  • Download ($42.00)
  • Cite this Item
Preview not available
Preview not available

Abstract

γ-Aminobutyrate transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, the previously identified Arabidopsis thaliana (L.) Heyhn GABA-T (AtGABA-T) was characterized in more detail. Full-length AtGABA-T contains an N-terminal 36 amino acid long targeting pre-sequence (36 amino acids) that is both sufficient and necessary for targeting the enzyme to mitochondria. Removal of the pre-sequence encoding this N-terminal targeting domain and co-expression of the resulting truncated AtGABA-T cDNA with the GroES/EL molecular chaperone complex in Escherichia coli yielded good recovery of the soluble recombinant proteins. Activity assays indicated that purified recombinant GABA-T has both pyruvate- and glyoxylate-dependent activities, but cannot utilize 2-oxoglutarate as amino acceptor. Kinetic parameters for glyoxylate- and pyruvate-dependent GABA-T activities were similar, with physiologically relevant affinities. Assays of GABA-T activity in cell-free leaf extracts from wild-type Arabidopsis and two knockout mutants in different genetic backgrounds confirmed that the native enzyme possesses both pyruvate- and glyoxylate-dependent activities. The GABA-T transcript was present throughout the plant, but its expression was highest in roots and increased as a function of leaf development. A GABA-T with dual functions suggests the potential for interaction between GABA metabolism and photorespiratory glyoxylate production.

Page Thumbnails

  • Thumbnail: Page 
[1743]
    [1743]
  • Thumbnail: Page 
1744
    1744
  • Thumbnail: Page 
1745
    1745
  • Thumbnail: Page 
1746
    1746
  • Thumbnail: Page 
1747
    1747
  • Thumbnail: Page 
1748
    1748
  • Thumbnail: Page 
1749
    1749
  • Thumbnail: Page 
1750
    1750
  • Thumbnail: Page 
1751
    1751
  • Thumbnail: Page 
1752
    1752
  • Thumbnail: Page 
1753
    1753
  • Thumbnail: Page 
1754
    1754
  • Thumbnail: Page 
1755
    1755
  • Thumbnail: Page 
1756
    1756
  • Thumbnail: Page 
1757
    1757