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Abstract <p>γ-Hydroxybutyrate dehydrogenase (GHBDH) is an enzyme belonging to the oxidoreductase class, catalyzing the reversible conversion of succinic semialdehyde (SSA) to γ-hydroxybutyric acid (GHB). It has been established that, in maize seedlings, GHBDH has mitochondrial (73.7%) and cytoplasmic localization (26.3%). Two homogeneous preparations of GHBDH isoforms were obtained from 7-day-old maize seedlings. The purified GHBDH1 preparation had a native molecular mass of 60.3 kDa (<i>Mr</i> of individual subunits ~15&#xa0;kDa). GHBDH2, a heteromer with a molecular mass of ~286 kDa, consisted of subunits with <i>Mr</i> ranging from 52 to 66 kDa. The optimal pH values for the obtained enzymes differed: for GHBDH1, the optimum pH for the oxidation reaction of γ-hydroxybutyrate was 9.0, while for GHBDH2, the optimum pH was 7.0. The kinetics of the enzymatic reaction of GHB conversion to succinic semialdehyde follows the Michaelis–Menten equation. The Km value for GHBDH1 with γ-hydroxybutyric acid was 0.31 ± 0.01 mM, and for NAD<sup>+</sup> it was 0.47&#xa0;mM ± 0.02. For GHBDH2, the <i>K</i><sub>m</sub> value with the substrate GHB was 0.7 ± 0.03 mM, and the <i>K</i><sub>m</sub> value for NAD<sup>+</sup> was 0.19 ± 0.01 mM. It was shown that CaCl<sub>2</sub> and KCl increased the activity of GHBDH1, while MgCl<sub>2</sub> had a minor inhibitory effect. The catalytic activity of GHBDH2 increased in the presence of CaCl<sub>2</sub>, KCl, and MgCl<sub>2</sub>. The study has both fundamental significance, expanding knowledge about the properties of GHBDH and its role in plant cell metabolism, and applied significance, since data on the mechanisms of regulation of GHBDH work can be used to develop methods for increasing the productivity and resistance of plants to unfavorable environmental factors.</p>

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Physicochemical and Catalytic Properties of Homogeneous Isoforms of γ-Hydroxybutyrate Dehydrogenase from Maize (Zea mays L.)

  • 期刊论文

  • 发表日期：

    2025年6月13日

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  • G. B. Anokhina,
  • E. V. Plotnikova,
  • A. T. Eprintsev

摘要

Abstract

γ-Hydroxybutyrate dehydrogenase (GHBDH) is an enzyme belonging to the oxidoreductase class, catalyzing the reversible conversion of succinic semialdehyde (SSA) to γ-hydroxybutyric acid (GHB). It has been established that, in maize seedlings, GHBDH has mitochondrial (73.7%) and cytoplasmic localization (26.3%). Two homogeneous preparations of GHBDH isoforms were obtained from 7-day-old maize seedlings. The purified GHBDH1 preparation had a native molecular mass of 60.3 kDa (Mr of individual subunits ~15 kDa). GHBDH2, a heteromer with a molecular mass of ~286 kDa, consisted of subunits with Mr ranging from 52 to 66 kDa. The optimal pH values for the obtained enzymes differed: for GHBDH1, the optimum pH for the oxidation reaction of γ-hydroxybutyrate was 9.0, while for GHBDH2, the optimum pH was 7.0. The kinetics of the enzymatic reaction of GHB conversion to succinic semialdehyde follows the Michaelis–Menten equation. The Km value for GHBDH1 with γ-hydroxybutyric acid was 0.31 ± 0.01 mM, and for NAD+ it was 0.47 mM ± 0.02. For GHBDH2, the Km value with the substrate GHB was 0.7 ± 0.03 mM, and the Km value for NAD+ was 0.19 ± 0.01 mM. It was shown that CaCl2 and KCl increased the activity of GHBDH1, while MgCl2 had a minor inhibitory effect. The catalytic activity of GHBDH2 increased in the presence of CaCl2, KCl, and MgCl2. The study has both fundamental significance, expanding knowledge about the properties of GHBDH and its role in plant cell metabolism, and applied significance, since data on the mechanisms of regulation of GHBDH work can be used to develop methods for increasing the productivity and resistance of plants to unfavorable environmental factors.