REGULATION OF NITROGEN ASSIMILATION IN SACCHAROMYCES-CEREVISIAE - ROLES OF THE URE2 AND GLN3 GENES
REGULATION OF NITROGEN ASSIMILATION IN SACCHAROMYCES-CEREVISIAE - ROLES OF THE URE2 AND GLN3 GENES
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DOI：
10.1128/jb.170.2.708-713.1988
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发表时间：
1988-02-01
影响因子：
3.2
通讯作者：
MAGASANIK, B
中科院分区：
文献类型：
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作者：
COURCHESNE, WE;MAGASANIK, B
GLN 3基因的突变阻止了谷氨酸生长的酿酒酵母细胞中NAD-谷氨酸脱氢酶和谷氨酰胺合成酶水平的正常增加，而URE 2基因的突变导致谷氨酸和谷氨酰胺生长的细胞中这些酶的高水平。尿素2谷氨酰胺3双突变体在谷氨酸和谷氨酰胺上生长的细胞中具有低水平的谷氨酸脱氢酶和谷氨酰胺合成酶;因此，谷氨酰胺3突变对尿素2突变是上位性的。结果表明，在不存在功能性URE 2产物的情况下，GLN 3产物能够促进酶水平的增加，并且URE 2产物拮抗GLN 3产物。URE 2和GLN 3基因也被发现可以调节酶的活性水平。这种调节完全独立于底物诱导对酶的调节。谷氨酸脱氢酶，谷氨酰胺合成酶，和谷氨酸脱氢酶的活性较高的细胞上生长的谷氨酸作为氮源比在氮限制条件下生长的细胞。先前已经表明，这些酶的水平可以通过谷氨酰胺剥夺而增加。我们建议，URE 2-GLN 3系统调节酶的合成，响应谷氨酰胺和谷氨酸，调节细胞内氨的浓度，以保持谷氨酰胺在最佳生长所需的水平。
Mutations in the GLN3 gene prevented a normal increase in the NAD-glutamate dehydrogenase and glutamine synthetase levels in glutamate-grown Saccharomyces cerevisiae cells, whereas mutations in the URE2 gene resulted in high levels of these enzymes in glutamate- and glutamine-grown cells. A ure2 gln3 double mutant had low levels of glutamate dehydrogenase and glutamine synthetase in cells grown on glutamate and glutamine; thus, gln3 mutations were epistatic to the ure2 mutations. The results suggest that the GLN3 product is capable of promoting increases in enzyme levels in the absence of a functional URE2 product and that the URE2 product antagonizes the GLN3 product. The URE2 and GLN3 genes were also found to regulate the level of arginase activity. This regulation is completely independent of the regulation of arginase by substrate induction. The activities of glutamate dehydrogenase, glutamine synthetase, and arginase were higher in cells grown on glutamate as the nitrogen source than they were in cells grown under a nitrogen-limiting condition. It had previously been shown that the levels of these enzymes can be increased by glutamine deprivation. We propose that the URE2-GLN3 system regulates enzyme synthesis, in response to glutamine and glutamate, to adjust the intracellular concentration of ammonia so as to maintain glutamine at the level required for optimal growth.