Spectrophotometric assay of d-isoleucine using an artificially created d-amino acid dehydrogenase

Hironaga Akita, Yoshifumi Imaizumi, Hirokazu Suzuki, Katsumi Doi, Toshihisa Ohshima

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7 Citations (Scopus)


d-isoleucine (d-Ile) can be assayed using chiral chromatography but the availability of that method is limited by the necessity for special expertise and expensive equipment. We therefore developed a simple and specific colorimetric assay system for d-Ile determination using an artificially created NADP+-dependent d-amino acid dehydrogenase (DAADH). The system consists of two reaction steps: the first is the quantitative conversion of d-Ile to (3R)-2-oxo-3-methyl valerate by DAADH in which NADP+ is converted to NADPH, while the second is chemical conversion of NADPH to reduced water-soluble Tetrazolium-3 via a redox mediator. d-Ile was determined from 1 to 50 µM, and the assay was unaffected by the presence of any of three other isomers (100 µM), alcohol and organic acids.

Original languageEnglish
Pages (from-to)2245-2248
Number of pages4
JournalBiotechnology letters
Issue number11
Publication statusPublished - Nov 2014

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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