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Protein Engineering Studies on Structure and Function of Amino Acid Dehydrogenase

Research Project

Project/Area Number 02680159
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field 代謝生物化学
Research InstitutionGrant-in-Aid for Scientific Research (c)

Principal Investigator

TANIZAWA Katsuyuki  Osaka University, Institute of Scientific and Industrial Research, Associate Professor, 産業科学研究所, 助教授 (20133134)

Co-Investigator(Kenkyū-buntansha) HUKUI Toshio  Osaka University, Institute of Scientific and Industrial Research, Professor, 産業科学研究所, 教授 (90029843)
Project Period (FY) 1990 – 1991
Project Status Completed (Fiscal Year 1991)
Budget Amount *help
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1991: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1990: ¥1,300,000 (Direct Cost: ¥1,300,000)
KeywordsAmino Acid Dehydrogenase / Chemical Modification / Pyridoxal Phosphate / Active Site / Site-directed Mutagenesis (6) / ロイシン脱水素酵素 / 耐熱性酵素 / ピリドキサル5'ーリン酸 / リジン残基
Research Abstract

The following results have been obtained by the present studies.
(a)Identification of an Active-Site Lysine in Leucine Dehydrogenase by Chemical Modification with Pyridoxal Phosphate
Leucine dehydrogenase from Bacillus stearothermophilus was inactivated by incubation with pyridoxal 5'-phosphate(PLP)followed by reduction with sodium borohydride. The inactivation was completely retarded in the copresence of L-leucine and NAD^+. Several PLP molecules were indeed incorporated into one mol of the enzyme subunit concomitantly with the inactivation. Sequence analysis of the fluorescent peptides isolated from a proteolytic digest of the labeled protein revealed that Lys80, Lys91, Lys206, and Lys265 were labeled. Lys8O was most predominantly labeled and, in the presence of L-leucine and NAD^+, was specifically protected from the labeling. Furthermore, a linear relationship of about 1 : 1 was observed between the residual activity and the amount of PLP incorporated into Lys8O. Lys8O is conserved
(b … More )Functional Analysis of Active-Site Lysine 80 in Leucine Dehydrogenase by Site-Directed Mutagenesis
Lys80 of leucine dehydrogenase has been replaced by Ala, Arg, or Gln by sitedirected mutagenesis. The Lys8O mutant enzymes purified to homogeneity showed markedly low V values(0.2-1.6% of that of the wild-type enzyme)in the oxidative deamination, but variable_<max> values in the reductive amination(Lys8O-Ala, 89% ; Lys8O-Gln, 23% ; and Lys8O-Arg, 0.4% of that of the wild-type enzyme). The Lys8O-Ala and Lys8O-Gln mutant enzymes exhibited considerably increased K_m values for alpha-keto-iso-caproate, whereas the K_m values for NAD^+ and NADH of all the mutant enzymes were similar to those of the wild-type enzyme. iso-Caproate, a non-substrate analogue of alpha-keto-iso-caproate, competitively inhibited the reaction of both the wild-type and Lys8O-Ala mutant enzymes with K_i values much higher than the K_m value for alpha-keto-iso-caproate of the wild-type enzyme, suggesting the importance of an electrostatic interaction between the *-amino group of Lys8O and the alpha-carbonyl group of alpha-keto-iso-caproate in the binding of the keto acid substrate. Exogenously added primary amines including ammonium ion remarkably accelerated the reaction catalyzed by the Lys8OAla mutant enzyme, indicating that the added amines can partially replace the function of *-amino group of Lys8O depending on both their basicities (pK_a values) and molecular volumes. These results lead to the conclusion that the *-amino group of the active site Lys8O ftinctions as a general acid-base group in the catalysis of leucine dehyarogenase. Less

Report

(3 results)
  • 1991 Annual Research Report   Final Research Report Summary
  • 1990 Annual Research Report
  • Research Products

    (7 results)

All Other

All Publications (7 results)

  • [Publications] Takahiro Matsuyama: "Leucine Dehydrogenase from Bacillus stearothermophilus:Identification of Active-Site Lysine Residue by Chemical Modification with Pyridoxal Phosphate." J.Biochem.(1992)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1991 Final Research Report Summary
  • [Publications] Katsuyuki Tanizawa: "Chemical and Kinetic Evidence for the Essential Lysine 80 in Leucine Dehydrogenase from Bacillus stearothermophilus." J.Biol.Chem.(1992)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1991 Final Research Report Summary
  • [Publications] Takahiro Matsuyama, Katsuyuki Tanizawa, Kenji Soda, and Toshio Fukui: "Leucine Dehydrogenase from Bacillus stearothermophilus : Identification of Active-Site Lysine Residue by Chemical Modification with Pyridoxal Phosphate." J. Biochem.(1992)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1991 Final Research Report Summary
  • [Publications] Katsuyuki Tanizawa, Takahiro Matsuyama, and Toshio Fukui: "Chemical and Kinetic Evidence for the Essential Lysine 80 in Leucine Dehydrogenase from Bacillus stearothermophilus." J. Biol. Chem.(1992)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1991 Final Research Report Summary
  • [Publications] Takahiro Matsuyama: "Leucine Dehydrogenase from Bacillus stearothermophilus:Identification of ActiveーSite Lysine Residue by Chemical Modification with Pyridoxal Phosphate." J.Biochem.(1992)

    • Related Report
      1991 Annual Research Report
  • [Publications] Katsuyuki Tanizawa: "Chemical and Kinetic Evidevce for the Essential Lysine 80 in Levcine Dehydrogenase from Bacillus Stearothermophilu" J.Biol.Chem. (1992)

    • Related Report
      1991 Annual Research Report
  • [Publications] Katsuyuki Tanizawa: "Chemical and Kinetic Evidence for an Essential Lysine in the Thermostable Leucine Dehydrogenase from Bacillus stearothermophilus" Journal of Biological Chemistry. (1991)

    • Related Report
      1990 Annual Research Report

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Published: 1990-04-01   Modified: 2016-04-21  

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