Ishidoh K, Kominami E
Department of Biochemistry, Juntendo University School of Medicine, Tokyo, Japan.
FEBS Lett. 1994 Oct 3;352(3):281-4. doi: 10.1016/0014-5793(94)00924-4.
The proteolytic processes involved in the conversion of procathepsin L to cathepsin L on a negatively charged surface, dextran sulfate, were studied. Upon incubation for 30 min at 37 degrees C, pH 5.5 with dextran-sulfate and dithiothreitol, purified procathepsin L showed maximal activation and, correspondingly, the complete conversion to the 30 kDa, single chain mature form of enzyme was observed. In contrast, incubation under the same conditions on ice rather than at 37 degrees C for 30 or 60 min resulted in partial proteolysis to produce a 31 kDa form without a significant increase in activity. Amino terminal amino acid sequence analyses showed that the 30 kDa form obtained by incubation at 37 degrees C corresponds to the purified form of mature cathepsin L with a 2 amino acid extension at the amino terminal, and that the 31 kDa form generated by incubation on ice possesses a 6 amino acid amino terminal extension, suggesting that the activation and processing of procathepsin L are different processes, and that 4 amino acid residues (Glu-Pro-Leu-Met) at the carboxyterminal in the propeptide function to prevent the activation of processed cathepsin L.
研究了在带负电荷的表面葡聚糖硫酸酯上，组织蛋白酶原L转化为组织蛋白酶L所涉及的蛋白水解过程。在37℃、pH 5.5条件下，将纯化的组织蛋白酶原L与葡聚糖硫酸酯和二硫苏糖醇一起孵育30分钟后，其显示出最大活化，相应地，观察到其完全转化为30 kDa的单链成熟酶形式。相比之下，在相同条件下于冰上而非37℃孵育30或60分钟会导致部分蛋白水解，产生一种31 kDa的形式，但其活性没有显著增加。氨基末端氨基酸序列分析表明，在37℃孵育获得的30 kDa形式对应于成熟组织蛋白酶L的纯化形式，其氨基末端有2个氨基酸延伸，而在冰上孵育产生的31 kDa形式具有6个氨基酸的氨基末端延伸，这表明组织蛋白酶原L的活化和加工是不同的过程，并且前肽中羧基末端的4个氨基酸残基（Glu-Pro-Leu-Met）起到防止加工后的组织蛋白酶L活化的作用。
