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B6db references: 29352105

type Journal Article
authors Zheng RC, Hachisuka SI, Tomita H, Imanaka T, Zheng YG, Nishiyama M, Atomi H
title An ornithine ω-aminotransferase required for growth in the absence of exogenous proline in the archaeon Thermococcus kodakarensis
journal J Biol Chem
sel selected
ui 29352105
year (2018)
volume 293
number 10
pages 3625-3636
keywords amino acid; aminotransferase; archaea; biosynthesis; enzyme; metabolism; ornithine; proline; thermophile; transamination
abstract Aminotransferases are pyridoxal 5'-phosphate-dependent enzymes that catalyze reversible transamination reactions between amino acids and α-keto acids, and are important for the cellular metabolism of nitrogen. Many bacterial and eukaryotic ω-aminotransferases that use L-ornithine (Orn), L-lysine (Lys) or γ-aminobutyrate (GABA) have been identified and characterized, but the corresponding enzymes from archaea are unknown. Here we examined the activity and function of TK2101, a gene annotated as GABA aminotransferase, from the hyperthermophilic archaeon Thermococcus kodakarensis We overexpressed the TK2101 gene in T. kodakarensis and purified and characterized the recombinant protein and found that it displays only low levels of GABA aminotransferase activity. Instead, we observed a relatively high ω-aminotransferase activity with L-Orn and L-Lys as amino donors. The most preferred amino acceptor was 2-oxoglutarate. To examine the physiological role of TK2101, we created a TK2101 gene-disruption strain (ΔTK2101), which was auxotrophic for proline. Growth comparison with the parent strain KU216 and the biochemical characteristics of the protein strongly suggested that TK2101 encodes an Orn aminotransferase involved in the biosynthesis of L-Pro. Phylogenetic comparisons of the TK2101 sequence with related sequences retrieved from the databases revealed the presence of several distinct protein groups, some of which having no experimentally studied member. We conclude that TK2101 is part of a novel group of Orn aminotransferases that are widely distributed at least in the genus Thermococcus, but perhaps also throughout the Archaea.
last changed 2018/04/03 14:46

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