type	Journal Article
authors	Fujitani, Y.; Nakajima, N.; Ishihara, K.; Oikawa, T.; Ito, K.; Sugimoto, M.
title	Molecular and biochemical characterization of a serine racemase from Arabidopsis thaliana
journal	Phytochemistry
Activity	5.1.1.18
Family	5.1.1.18
sel	selected
ui	16483618
year	(2006)
volume	67
number	7
pages	668-674
keywords	Alanine Racemase/metabolism
abstract	A cDNA encoding a homolog of mammalian serine racemase, a unique enzyme in eukaryotes, was isolated from Arabidopsis thaliana and expressed in Escherichia coli cells. The gene product, of which the amino acid residues for binding pyridoxal 5'-phosphate (PLP) are conserved in this as well as mammalian serine racemases, catalyzes not only serine racemization but also dehydration of serine to pyruvate. The enzyme is a homodimer and requires PLP and divalent cations, Ca(2+), Mg(2+), Mn(2+), Fe(2+), or Ni(2+), at alkaline pH for both activities. The racemization process is highly specific toward l-serine, whereas l-alanine, l-arginine, and l-glutamine were poor substrates. The V(max)/K(m) values for racemase activity of l- and d-serine are 2.0 and 1.4nmol/mg/min/mM, respectively, and those values for l- and d-serine on dehydratase activity are 13 and 5.3nmol/mg/min/mM, i.e. consistent with the theory of racemization reaction and the specificity of dehydration toward l-serine. Hybridization analysis showed that the serine racemase gene was expressed in various organs of A. thaliana.
last changed	2016/10/06 17:17