Hohmann S, Cederberg H
Institut für Mikrobiologie, Technische Hochsuchule Darmstadt, Federal Republic of Germany.
Eur J Biochem. 1990 Mar 30;188(3):615-21. doi: 10.1111/j.1432-1033.1990.tb15442.x.
Recently we deleted the pyruvate decarboxylase structural gene PDC1 from the genome of the yeast Saccharomyces cerevisiae. The pdc1 deletion mutants had pyruvate decarboxylase activity due to the presence of a second structural gene [Schaaff, I., Green, J. B. A., Gozalbo, D. & Hohmann, S. (1989) Curr. Genet. 15, 75-81]. We cloned and sequenced this gene which we call PDC5. The predicted amino acid sequences of PDC1 and PDC5 are 88% identical. Deletion of PDC5 did not cause any decrease in the specific pyruvate decarboxylase activity while pdc1 deletion mutants had 80% of the wild-type activity. Deletion mutants lacking both PDC1 and PDC5 did not show any detectable pyruvate decarboxylase activity in vitro and were unable to ferment glucose. This indicates that PDC1 and PDC5 are the only structural genes for pyruvate decarboxylase in yeast. The PDC5 isoenzyme showed a slightly higher Km value for its substrate pyruvate than the PDC1 product (PDC5: Km = 8 mM; PDC1: Km = 5 mM), as measured in crude extract of pdc1 and pdc5 deletion mutants, respectively. PDC5 is only expressed in pdc1 deletion mutants. No mRNA transcribed from PDC5 could be detected in wild-type cells. Thus, in addition to the control by glucose induction, pyruvate decarboxylase activity seems to be subject to autoregulation. Similar phenomena have been described previously for tubulin, histones and a ribosomal protein but not for metabolic enzymes.
最近，我们从酿酒酵母基因组中删除了丙酮酸脱羧酶结构基因PDC1。由于存在第二个结构基因，pdc1缺失突变体具有丙酮酸脱羧酶活性[Schaaff, I., Green, J. B. A., Gozalbo, D. & Hohmann, S. (1989) Curr. Genet. 15, 75 - 81]。我们克隆并测序了这个基因，将其命名为PDC5。PDC1和PDC5的预测氨基酸序列有88%的同一性。删除PDC5并没有导致丙酮酸脱羧酶比活性的任何降低，而pdc1缺失突变体具有野生型活性的80%。同时缺乏PDC1和PDC5的缺失突变体在体外没有显示出任何可检测到的丙酮酸脱羧酶活性，并且无法发酵葡萄糖。这表明PDC1和PDC5是酵母中丙酮酸脱羧酶仅有的结构基因。在分别来自pdc1和pdc5缺失突变体的粗提取物中测量时，PDC5同工酶对其底物丙酮酸的Km值略高于PDC1产物（PDC5：Km = 8 mM；PDC1：Km = 5 mM）。PDC5仅在pdc1缺失突变体中表达。在野生型细胞中未检测到从PDC5转录的mRNA。因此，除了受葡萄糖诱导的调控外，丙酮酸脱羧酶活性似乎还受到自身调节。先前已针对微管蛋白、组蛋白和一种核糖体蛋白描述过类似现象，但未针对代谢酶描述过。
