Nonstereospecific transamination catalyzed by pyridoxal phosphate- dependent amino acid racemases of broad substrate specificity

Young Hee Lim, Tohru Yoshimura, Yoichi Kurokawa, Nobuyoshi Esaki, Kenji Soda

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Pyridoxal 5'-phosphate-dependent amino acid racemases of broad substrate specificity catalyze transamination as a side reaction. We studied the stereospecificities for hydrogen abstraction from C-4' of the bound pyridoxamine 5'-phosphate during transamination from pyridoxamine 5'- phosphate to pyruvate catalyzed by three amino acid racemases of broad substrate specificity. When the enzymes were incubated with (4'S)- or (4'R)- [4'-3H]pyridoxamine 5'-phosphate in the presence of pyruvate, tritium was released into the solvent from both pyridoxamine 5'-phosphates. Thus, these enzymes abstract a hydrogen nonstereospecifically from C-4' of the coenzyme in contrast to the other pyridoxal 5'-phosphate-dependent enzymes so far studied, which catalyze the stereospecific hydrogen removal. Amino acid racemase of broad substrate specificity from Pseudomonas putida produced D- and L-glutamate from α-ketoglutarate through the transamination with L- ornithine. Because glutamate does not serve as a substrate for racemization, the enzyme catalyzed the nonstereospecific overall transamination between L- ornithine and α-ketoglutarate. The cleavage and formation of the C-H bond at C-4' of the coenzyme and C-2 of the substrate thus occurs nonstereospecifically on both sides of the plane of the coenzyme-substrate complex intermediate. Amino acid racemase of broad substrate specificity is the first example of a pyridoxal enzyme catalyzing nonstereospecific transamination.

Original languageEnglish
Pages (from-to)4001-4005
Number of pages5
JournalJournal of Biological Chemistry
Volume273
Issue number7
DOIs
Publication statusPublished - 1998 Feb 13
Externally publishedYes

Fingerprint

Amino Acid Isomerases
Pyridoxal Phosphate
Substrate Specificity
Pyridoxamine
Coenzymes
Substrates
Enzymes
Hydrogen
Phosphates
Pyruvic Acid
Glutamic Acid
Pyridoxal
Pseudomonas putida
Ornithine
Tritium
pyridoxamine phosphate

ASJC Scopus subject areas

  • Biochemistry

Cite this

Nonstereospecific transamination catalyzed by pyridoxal phosphate- dependent amino acid racemases of broad substrate specificity. / Lim, Young Hee; Yoshimura, Tohru; Kurokawa, Yoichi; Esaki, Nobuyoshi; Soda, Kenji.

In: Journal of Biological Chemistry, Vol. 273, No. 7, 13.02.1998, p. 4001-4005.

Research output: Contribution to journalArticle

Lim, Young Hee ; Yoshimura, Tohru ; Kurokawa, Yoichi ; Esaki, Nobuyoshi ; Soda, Kenji. / Nonstereospecific transamination catalyzed by pyridoxal phosphate- dependent amino acid racemases of broad substrate specificity. In: Journal of Biological Chemistry. 1998 ; Vol. 273, No. 7. pp. 4001-4005.
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