MOLECULAR ANALYSIS OF GPH1, THE GENE ENCODING GLYCOGEN-PHOSPHORYLASE IN SACCHAROMYCES-CEREVISIAE
MOLECULAR ANALYSIS OF GPH1, THE GENE ENCODING GLYCOGEN-PHOSPHORYLASE IN SACCHAROMYCES-CEREVISIAE
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DOI：
10.1128/mcb.9.4.1659
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发表时间：
1989-04-01
影响因子：
5.3
通讯作者：
FLETTERICK, RJ
中科院分区：
文献类型：
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作者：
HWANG, PK;TUGENDREICH, S;FLETTERICK, RJ
在酵母细胞中，糖原磷酸化酶的活性受到环 AMP 介导的酶磷酸化的调节。我们之前已经克隆了酿酒酵母糖原磷酸化酶 (GPH 1) 的基因。为了评估糖原和磷酸化酶催化的糖原分解在酵母生命周期中的作用，构建了缺乏功能性 GPH1 基因或含有该基因的多个拷贝的酵母菌株。发现 GPH1 不是酵母细胞中的必需基因。 GPH1 中破坏的单倍体细胞缺乏磷酸化酶活性，细胞内糖原水平较高，但其他方面与野生型细胞相似。破坏纯合的二倍体细胞能够形成孢子并产生有活力的子囊孢子。功能性 GPH1 的缺失不会损害细胞合成和储存海藻糖。在携带多个含有 GPH1 的 2.mu.m 质粒的细胞中检测到磷酸化酶活性增加了 10 至 40 倍。 Northern (RNA) 分析表明，GPH1 转录在指数生长期后期被诱导，几乎与细胞内糖原积累的开始同时发生。因此，指数细胞中糖原的低水平主要不是通过调节磷酸化酶组成量的磷酸化状态来维持的。 GPH1 似乎没有受到正式的葡萄糖抑制，因为转录诱导发生在培养基中葡萄糖耗尽之前。
In yeast cells, the activity of glycogen phosphorylase is regulated by cyclic AMP-mediated phosphorylation of the enzyme. We have previously cloned the gene for glycogen phosphorylase (GPH 1) Saccharomyces cerevisiae. To assess the role of glycogen and phosphorylase-catalyzed glycogenolysis in the yeast life cycle, yeast strains lacking a functional GPH1gene or containing multiple copies of the gene were constructed. GPH1 was found not to be an essential gene in yeast cells. Haploid cells disrupted in GPH1 lacked phosphorylase activity and attained higher levels of intracellular glycogen but otherwise were similar to wild-type cells. Diploid cells homozygous for the disruption were able to sporulate and give rise to viable ascospores. Absence of functional GPH1 did not impair cells from synthesizing and storing trehalose. Increases in phosphorylase activity of 10- to 40-fold were detected in cells carrying multiple copies of GPH1-containing 2.mu.m plasmid. Northern (RNA) analysis indicated that GPH1 transcription was induced at the late exponential growth phase, almost simultaneous with the onset of intracellular glycogen accumulation. Thus, the low level of glycogen in exponential cells was not primarily maintained through regulating the phosphorylation state of a constitutive amount of phosphorylase. GPH1 did not appear to be under formal glucose repression, since transcriptional induction occurred well in advance of glucose depletion from the medium.