热稳定性
氧化还原酶
生物化学
氨基酸
酶
辅因子
化学
脱氢酶
NAD+激酶
生物
作者
Hideyuki Yamaguchi,Akiko Kamegawa,Kengo Nakata,Tatsuki Kashiwagi,Yoshinori Fujiyoshi,Kazuhide Tani,Toshimi Mizukoshi
出处
期刊:Sub-cellular biochemistry
日期:2020-12-01
卷期号:: 355-372
被引量:1
标识
DOI:10.1007/978-3-030-58971-4_10
摘要
Thermostability is a key factor in the industrial and clinical application of enzymes, and understanding mechanisms of thermostability is valuable for molecular biology and enzyme engineering. In this chapter, we focus on the thermostability of leucine dehydrogenase (LDH, EC 1.4.1.9), an amino acid-metabolizing enzyme that is an NAD+-dependent oxidoreductase which catalyzes the deamination of branched-chain l-amino acids (BCAAs). LDH from Geobacillus stearothermophilus (GstLDH) is a highly thermostable enzyme that has already been applied to quantify the concentration of BCAAs in biological specimens. However, the molecular mechanism of its thermostability had been unknown because no high-resolution structure was available. Here, we discuss the thermostability of GstLDH on the basis of its structure determined by cryo-electron microscopy. Sequence comparison with other structurally characterized LDHs (from Lysinibacillus sphaericus and Sporosarcina psychrophila) indicated that non-conserved residues in GstLDH, including Ala94, Tyr127, and the C-terminal region, are crucial for oligomeric stability through intermolecular interactions between protomers. Furthermore, NAD+ binding to GstLDH increased the thermostability of the enzyme as additional intermolecular interactions formed on cofactor binding. This knowledge is important for further applications and development of amino acid metabolizing enzymes in industrial and clinical fields.
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