Glutamate Dehydrogenase Functions in Glutamic Acid Metabolism and Stress Resistance in <i>Pyropia haitanensis</i>
<i>Pyropia haitanensis</i> is an important laver species in China. Its quality traits are closely related to the content of glutamic acid. Glutamate dehydrogenase (GDH) is a crucial enzyme in the glutamic acid metabolism. In this study, two <i>GDH</i> genes from <i>P. h...
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| Autores principales: | , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/a749fa1dc9eb4373824a32d4e9725ebd |
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| Sumario: | <i>Pyropia haitanensis</i> is an important laver species in China. Its quality traits are closely related to the content of glutamic acid. Glutamate dehydrogenase (GDH) is a crucial enzyme in the glutamic acid metabolism. In this study, two <i>GDH</i> genes from <i>P. haitanensis</i>, <i>PhGDH</i>1 and <i>PhGDH</i>2, were cloned and successfully expressed in <i>Escherichia coli</i>. The in vitro enzyme activity assay demonstrated that the catalytic activity of PhGDHs is mainly in the direction of ammonium assimilation. The measured <i>K<sub>m</sub></i> values of PhGDH1 for NADH, (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>, and α-oxoglutarate were 0.12, 4.99, and 0.16 mM, respectively, while the corresponding <i>K<sub>m</sub></i> values of PhGDH2 were 0.02, 3.98, and 0.104 mM, respectively. Site-directed mutagenesis results showed that Gly<sup>193</sup> and Thr<sup>361</sup> were important catalytic residues for PhGDH2. Moreover, expression levels of both PhGDHs were significantly increased under abiotic stresses. These results suggest that PhGDHs can convert α-oxoglutarate to glutamic acid, and enhance the flavor and stress resistance of <i>P. haitanensis</i>. |
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