D-Serine dehydratase from chicken kidney: a vertebral homologue of the cryptic enzyme from Burkholderia cepacia.
D-serine dehydratase (DSD) catalyses the conversion of d-serine to pyruvate and ammonia. d-Serine is a physiological modulator of glutamate neurotransmission in vertebrate brains. In mammals d-serine is degraded by d-amino-acid oxidase, whereas in chicken brain it is degraded by DSD, as we have recently demonstrated [Tanaka et al. (2007) Anal. Biochem. 362, 83-88]. To clarify the roles of DSD in avian species, we purified DSD from chicken kidney. The purified enzyme was a heterodimer consisting of subunits separable by SDS-PAGE but with identical N-terminal amino acid sequences. The prominent absorption at 416 nm and the inhibition of the enzyme both by hydroxylamine and by aminooxyacetate suggested that the enzyme contains pyridoxal 5'-phosphate as a cofactor. The enzyme showed the highest specificity to d-serine: the k(cat)/K(m) values of DSD for d-serine, d-threonine and l-serine were 6.19 x 10(3), 164 and 16 M(-1)s(-1), respectively. DSD was found immunohistochemically in the proximal tubules of the chicken kidney. Judging from the amino acid sequence deduced from the cDNA, chicken DSD is a homologue of cryptic DSD from Burkholderia cepacia and low-specificity d-threonine aldolase from Arthrobacter sp. strain DK-38, all of which have a cofactor binding motif of PHXK(T/A) in their N-terminal portions.
Tanaka
Hiroyuki
H
Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Seta, Ohtsu, Shiga 520-2192, Japan. tanakah@belle.shiga-med.ac.jp
Yamamoto
Atsushi
A
Ishida
Tetsuo
T
Horiike
Kihachiro
K
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry; D016956:Burkholderia cepacia / Q000201:enzymology; D002645:Chickens / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry; D006836:Hydro-Lyases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D030161:Avian Proteins; D001426:Bacterial Proteins; D018076:DNA, Complementary; D006836:Hydro-Lyases; C101950:D-serine dehydratase