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B6db references: 19264755

type Journal Article
authors Clark SM, Di Leo R, Dhanoa PK, Van Cauwenberghe OR, Mullen RT, Shelp BJ.
title Biochemical characterization, mitochondrial localization, expression, and potential functions for an Arabidopsis gamma-aminobutyrate transaminase that utilizes both pyruvate and glyoxylate
journal J Exp Bot
Activity gaba-t
Family 2.6.1.96
sel selected
ui 19264755
year (2009)
volume 60
number 6
pages 1743-57
 
keywords amino acceptor, gamma-aminobutyrate, gamma-aminobutyrate transaminase, protein purification, heterologous expression, recombinant protein.
abstract Gamma-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.
last changed 2014/02/14 11:40

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