Glutamate dehydrogenases (GDHs) are fundamental to cellular nitrogen and energy balance. Yet little is known about these enzymes in the oleaginous yeast Yarrowia lipolytica. The YALI0F17820g and YALI0E09603g genes, encoding potential GDH enzymes in this organism, were examined. Heterologous expression in gdh-null Saccharomyces cerevisiae and examination of Y. lipolytica strains carrying gene deletions demonstrate that YALI0F17820g (ylGDH1) encodes a NADP-dependent GDH whereas YALI0E09603g (ylGDH2) encodes a NAD-dependent GDH enzyme. The activity encoded by these two genes accounts for all measurable GDH activity in Y. lipolytica. Levels of the two enzyme activities are comparable during logarithmic growth on rich medium, but the NADP-ylGDH1p enzyme activity is most highly expressed in stationary and nitrogen starved cells by threefold to 12-fold. Replacement of ammonia with glutamate causes a decrease in NADP-ylGdh1p activity, whereas NAD-ylGdh2p activity is increased. When glutamate is both carbon and nitrogen sources, the activity of NAD-ylGDH2p becomes dominant up to 18-fold compared with that of NADP-ylGDH1p. Gene deletion followed by growth on different carbon and nitrogen sources shows that NADP-ylGdh1p is required for efficient nitrogen assimilation whereas NAD-ylGdh2p plays a role in nitrogen and carbon utilization from glutamate. Overexpression experiments demonstrate that ylGDH1 and ylGDH2 are not interchangeable. These studies provide a vital basis for future consideration of how these enzymes function to facilitate energy and nitrogen homeostasis in Y. lipolytica.

中文翻译：

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产油酵母解脂耶氏酵母中的谷氨酸脱氢酶。

谷氨酸脱氢酶（GDHs）是细胞氮和能量平衡的基础。对油性酵母解脂耶氏酵母中的这些酶知之甚少。检查了在该生物体中编码潜在的GDH酶的YALI0F17820g和YALI0E09603g基因。在gdh-null酿酒酵母中的异源表达和携带基因缺失的解脂耶氏酵母菌株的检测证明YALI0F17820g（ylGDH1）编码NADP依赖性GDH，而YALI0E09603g（ylGDH2）编码NAD依赖性GDH酶。这两个基因编码的活性占解脂耶氏酵母中所有可测量的GDH活性。在富培养基上对数生长期间，这两种酶的活性水平相当，但是在静止和氮饥饿的细胞中，NADP-ylGDH1p酶的活性最高表达了三倍至十二倍。用谷氨酸替代氨导致NADP-ylGdh1p活性降低，而NAD-ylGdh2p活性升高。当谷氨酸既是碳源又是氮源时，NAD-ylGDH2p的活性占主导地位，是NADP-ylGDH1p的18倍。基因缺失，然后在不同碳和氮源上生长表明，NADP-ylGdh1p是有效吸收氮所必需的，而NAD-ylGdh2p在谷氨酸的氮和碳利用中发挥作用。过表达实验表明ylGDH1和ylGDH2是不可互换的。这些研究为今后考虑这些酶如何发挥作用以促进解脂耶氏酵母中的能量和氮稳态提供了重要的基础。而NAD-ylGdh2p活性增加。当谷氨酸既是碳源又是氮源时，NAD-ylGDH2p的活性占主导地位，是NADP-ylGDH1p的18倍。基因缺失，然后在不同碳和氮源上生长表明，NADP-ylGdh1p是有效吸收氮所必需的，而NAD-ylGdh2p在谷氨酸的氮和碳利用中发挥作用。过表达实验表明ylGDH1和ylGDH2是不可互换的。这些研究为今后考虑这些酶如何发挥作用以促进解脂耶氏酵母中的能量和氮稳态提供了重要的基础。而NAD-ylGdh2p活性增加。当谷氨酸既是碳源又是氮源时，NAD-ylGDH2p的活性比NADP-ylGDH1p的活性高18倍。基因缺失，然后在不同碳和氮源上生长表明，NADP-ylGdh1p是有效吸收氮所必需的，而NAD-ylGdh2p在谷氨酸的氮和碳利用中发挥作用。过表达实验表明ylGDH1和ylGDH2是不可互换的。这些研究为今后考虑这些酶如何发挥作用以促进解脂耶氏酵母中的能量和氮稳态提供了重要的基础。基因缺失，然后在不同碳和氮源上生长表明，NADP-ylGdh1p是有效吸收氮所必需的，而NAD-ylGdh2p在谷氨酸的氮和碳利用中发挥作用。过表达实验表明ylGDH1和ylGDH2是不可互换的。这些研究为今后考虑这些酶如何发挥作用以促进解脂耶氏酵母中的能量和氮稳态提供了重要的基础。基因缺失，然后在不同碳和氮源上生长表明，NADP-ylGdh1p是有效吸收氮所必需的，而NAD-ylGdh2p在谷氨酸的氮和碳利用中发挥作用。过表达实验表明ylGDH1和ylGDH2是不可互换的。这些研究为今后考虑这些酶如何发挥作用以促进解脂耶氏酵母中的能量和氮稳态提供了重要的基础。