Journal of Biochemistry Advance Access published online on October 30, 2007
Journal of Biochemistry, doi:10.1093/jb/mvm203
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© 2007 The Japanese Biochemical Society
D-Serine Dehydratase from Chicken Kidney: a Vertebral Homologue of the Cryptic Enzyme from Burkholderia cepacia
Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Seta, Ohtsu, Shiga 520-2192
*To whom correspondence should be addressed: Hiroyuki Tanaka, Tel: +81-77-548-2158, Fax: +81-77-548-2157, E-mail: tanakah{at}belle.shiga-med.ac.jp
Received August 30, 2007; Accepted September 30, 2007
| Abstract |
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D-Serine dehydratase (DSD) catalyzes 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 kcat /Km values of DSD for D-serine, D-threonine, and L-serine were 6.19 x 103, 164, and 16 M–1s–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.
Key Words: D-serine, D-serine dehydratase, pyridoxal 5'-phosphate, chicken kidney, proximal tubules