3-Isopropylmalate dehydrogenase (IPMDH) catalyzes oxidative decarboxylation of (2R, 3S)-3-isopropylmalate to 2-oxoisocaproate in leucine biosynthesis. In this study, recombinant IPMDH (HjIPMDH) from an extremely halophilic archaeon, Haloarcula japonica TR-1, was characterized. Activity of HjIPMDH increased as KCl concentration increased, and the maximum activity was observed at 3.0 m KCl. Analytical ultracentrifugation revealed that HjIPMDH formed a homotetramer at high KCl concentrations, and it dissociated to a monomer at low KCl concentrations. Additionally, HjIPMDH was thermally stabilized by higher KCl concentrations. This is the first report on haloarchaeal IPMDH.

中文翻译：

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来自极嗜盐古生菌 Haloarcula japonica 的 3-异丙基苹果酸脱氢酶的表征。

3-异丙基苹果酸脱氢酶 (IPMDH) 在亮氨酸生物合成中催化 (2R, 3S)-3-异丙基苹果酸氧化脱羧为 2-氧代异己酸。在这项研究中，对来自极度嗜盐古细菌 Haloarcula japonica TR-1 的重组 IPMDH (HjIPMDH) 进行了表征。HjIPMDH 的活性随着 KCl 浓度的增加而增加，在 3.0 m KCl 时观察到最大活性。分析超速离心表明，HjIPMDH 在高氯化钾浓度下形成同源四聚体，在低氯化钾浓度下解离成单体。此外，HjIPMDH 通过较高的 KCl 浓度进行热稳定。这是关于卤代古菌 IPMDH 的第一份报告。