BIOSYNTHESIS OF VACUOLAR YEAST GLYCOPROTEIN CARBOXYPEPTIDASE-Y - CONVERSION OF PRECURSOR INTO ENZYME
BIOSYNTHESIS OF VACUOLAR YEAST GLYCOPROTEIN CARBOXYPEPTIDASE-Y - CONVERSION OF PRECURSOR INTO ENZYME
复制标题
DOI：
10.1111/j.1432-1033.1978.tb12275.x
复制
发表时间：
1978-01-01
期刊：
影响因子：
--
通讯作者：
TANNER, W
中科院分区：
文献类型：
--
作者：
HASILIK, A;TANNER, W
液泡糖蛋白羧肽酶Y [酿酒酵母]（Mr [相对分子量] 61，000）通过较大的前体（Mr 67，000）合成。约35%的前体蛋白质可以在细胞匀浆的沉淀级分中回收。大部分放射性可由针对羧肽酶Y的[兔]抗体沉淀[EC 3.4.12.-]随着前体转化为酶，从沉淀部分重新分配到可溶部分。前体蛋白与Hayashi等人先前描述的酶抑制剂复合物不同。放射性甘露糖掺入前体表明糖基化发生在多肽链合成完成之前或之后。前体在体外被胰蛋白酶转化为大小与羧肽酶Y相同的蛋白质。胰蛋白酶释放的额外片段可能含有4个苯丙氨酸和至少10个亮氨酸残基。在体外测试的3种酵母蛋白酶中，只有蛋白酶B催化前体转化为大小与羧肽酶Y相同的蛋白质。在体内的转换，这大概是一个例子，细胞内有限的蛋白水解，进行了约6分钟的半衰期。据推测，前体是一个无活性的前酶，procarboxypeptidase Y，而不是前酶，作为无活性的水解酶，它只存在于细胞内运输到液泡，在那里的前酶被激活所需的时间。
The vacuolar glycoprotein carboxypeptidase Y [Saccharomyces cerevisiae] (Mr [relative MW] 61,000) is synthesized via a larger precursor (Mr 67,000). About 35% of the precursor protein can be recovered in the sedimenting fraction of the cell homogenate. A large part of the radioactivity precipitable by [rabbit] antibodies directed against carboxypeptidase Y [EC 3.4.12.-] is redistributed from the sedimenting fraction into the soluble one as the precursor is converted to the enzyme. The precursor protein is not identical with the enzyme-inhibitor complex described previously by Hayashi et al. The incorporation of radioactive mannose into the precursor indicates that the glycosylation takes place before or immediately after the completion of the syntheses of the polypeptide chain. The precursor is converted by trypsin in vitro to a protein identical in size to carboxypeptidase Y. The extra piece released by trypsin probably contains 4 phenylalanine and at least 10 leucine residues. Of 3 yeast proteinases tested in vitro only the proteinase B catalyzed conversion of the precursor to a protein identical in size to carboxypeptidase Y. The conversion in vivo, which presumably is an example of intracellular-limited proteolysis, proceeds with a half-life of about 6 min. It is assumed that the precursor is an inactive pro-enzyme, procarboxypeptidase Y, rather than a pre-enzyme and that, as inactive hydrolase, it exists only during the time required for the intracellular transport to the vacuole, where the pro-enzyme is activated.