Alanine racemase activity in the microalga Thalassiosira sp.

Takehiko Yokoyama, Yumiko Tanaka, Minoru Sato, Nobuhiro Kan-No, Toshiki Nakano, Toshiyasu Yamaguchi, Eizoh Nagahisa

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)

    Abstract

    In this paper, the authors report the detection of alanine racemase activity in the marine diatom Thalassiosira sp. Since the Thalassiosira sp. was cultured under germ-free conditions, it appeared that D-alanine was not derived from bacteria but was produced through catalysis by algal alanine racemase. The rate of conversion of L-alanine to D-alanine was approximately the same as that for the reverse reaction, and the enzyme catalyzed the equilibration of the D- and L-forms. The crude enzyme preparation obtained from the cells at the stationary phase of the growth cycle had an optimal pH of approximately 9.5. The Lineweaver-Burk analysis showed that the Km for D- and L-alanine was 16.5 mM and 29.4 mM, respectively. It appears that the enzyme is highly specific for D- or L-alanine because it does not catalyze the racemization of other amino acids. In addition, after gel filtration, the enzyme did not require exogenous pyridoxal 5′-phosphate (PLP) for its activity, however, the effects of several chemicals suggest that the enzyme may be PLP-dependent. The enzyme is more similar to that found in invertebrates when compared with that found in bacteria. This is the first report on the occurrence of alanine racemase activity in the microalga Thalassiosira sp.

    Original languageEnglish
    Pages (from-to)924-930
    Number of pages7
    JournalFisheries Science
    Volume71
    Issue number4
    DOIs
    Publication statusPublished - 2005 Aug

    Keywords

    • Alanine racemase
    • D-alanine
    • D-amino acid
    • Diatom
    • Microalga
    • Thalassiosira

    ASJC Scopus subject areas

    • Aquatic Science

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