Brown J A, Segal H L, Maley F, Trimble R B, Chu F
J Biol Chem. 1979 May 25;254(10):3689-91.
The uptake by rat yolk sacs of native invertase and invertase which was deglycosylated by treatment with endo-beta-N-acetylglucosaminidase was compared. The initial rate of uptake of the deglycosylated enzyme was severalfold greater and its accumulation leveled off much earlier than that of the native enzyme. Uptake rates of the deglycosylated and native forms of the enzyme were proportional to their concentration in the medium in the range employed and were inhibited about 85% by 10(-6) M glucagon in both cases. After preloading of yolk sacs with native invertase, the tissue level of activity remained relatively constant over a subsequent 6-h time period, while with the deglycosylated form, activity declined substantially. Since this difference appears not to be attributable to differences in thermal stability, it is suggested that the deglycosylated form of the protein is more susceptible to intracellular proteolytic digestion. In vitro studies on the digestion of these two forms of invertase by trypsin are consistent with this suggestion.
比较了大鼠卵黄囊对天然转化酶以及经内切β-N-乙酰葡糖胺酶处理去糖基化的转化酶的摄取情况。去糖基化酶的初始摄取速率要高几倍，并且其积累比天然酶更早趋于平稳。在所采用的浓度范围内，去糖基化和天然形式的酶的摄取速率与其在培养基中的浓度成正比，并且在两种情况下均被10(-6)M胰高血糖素抑制约85%。用天然转化酶预先加载卵黄囊后，在随后的6小时时间段内，组织中的活性水平保持相对恒定，而对于去糖基化形式，活性则大幅下降。由于这种差异似乎不归因于热稳定性的差异，因此表明蛋白质的去糖基化形式更容易受到细胞内蛋白水解消化的影响。关于这两种形式的转化酶被胰蛋白酶消化的体外研究与这一推测一致。
