Schork S M, Thumm M, Wolf D H
Institut für Biochemie, Universität Stuttgart, Germany.
J Biol Chem. 1995 Nov 3;270(44):26446-50. doi: 10.1074/jbc.270.44.26446.
Catabolite inactivation of fructose-1,6-bisphosphatase (FBPase), a key enzyme in gluconeogenesis, is due to phosphorylation and subsequent degradation in the yeast Saccharomyces cerevisiae. The degradation process of the enzyme had been shown to depend on the action of the proteasome. Here we report that components of the ubiquitin pathway target FBPase to proteolysis. Upon glucose addition to yeast cells cultured on nonfermentable carbon sources FBPase is ubiquitinated in vivo. A multiubiquitin chain containing isopeptide linkages at Lys48 of ubiquitin is attached to FBPase. Formation of a multiubiquitin chain is a prerequisite for the degradation of FBPase. Catabolite degradation of FBPase is dependent on the ubiquitin-conjugating enzymes Ubc1, Ubc4, and Ubc5. The 26 S proteasome is involved in the degradation process.
果糖-1,6-二磷酸酶（FBPase）是糖异生途径中的关键酶，在酿酒酵母中，其分解代谢失活是由于磷酸化及随后的降解所致。该酶的降解过程已表明依赖于蛋白酶体的作用。在此我们报道，泛素途径的组分将FBPase靶向蛋白酶解。当向在非发酵碳源上培养的酵母细胞中添加葡萄糖时，FBPase在体内被泛素化。一条在泛素的赖氨酸48处含有异肽键的多聚泛素链连接到FBPase上。多聚泛素链的形成是FBPase降解的前提条件。FBPase的分解代谢降解依赖于泛素缀合酶Ubc1、Ubc4和Ubc5。26S蛋白酶体参与了降解过程。
