Rowan A D, Feng R, Konishi Y, Mort J S
Joint Diseases Laboratory, Shriners Hospital for Crippled Children, Montreal, Quebec, Canada.
Biochem J. 1993 Sep 15;294 ( Pt 3)(Pt 3):923-7. doi: 10.1042/bj2940923.
Electrospray mass spectrometric techniques were used to demonstrate that mature (single-chain) recombinant rat cathepsin B is capable of sequentially removing the three dipeptides which comprise the C-terminal extension of the proenzyme. A pepsin-cleaved form of a non-active mutant recombinant rat procathepsin B (Cys-29-Ser) was used as a 'substrate' to study C-terminal processing by mature cathepsin B. The results indicate that the first two residues (Arg-Phe) are removed efficiently, while the remaining four (Gln-Tyr-Trp-Gly), particularly the final two, are much more resistant to proteolysis. These cleavages were pronounced at pH 5.0 compared with pH 6.0, in agreement with the lower pH optimum for cathepsin B exopeptidase activity reported previously. From this example of the peptidyldipeptidase activity of cathepsin B we conclude that removal of the C-terminal extension may occur in any intracellular compartment where active cathepsin B is found.
采用电喷雾质谱技术来证明成熟的（单链）重组大鼠组织蛋白酶B能够依次去除构成该酶原C末端延伸部分的三个二肽。一种经胃蛋白酶切割的无活性突变重组大鼠组织蛋白酶原B（半胱氨酸-29-丝氨酸）形式被用作“底物”，以研究成熟组织蛋白酶B对C末端的加工过程。结果表明，前两个残基（精氨酸-苯丙氨酸）能被有效去除，而其余四个（谷氨酰胺-酪氨酸-色氨酸-甘氨酸），尤其是最后两个，对蛋白水解的抗性要强得多。与pH 6.0相比，在pH 5.0时这些切割更为明显，这与先前报道的组织蛋白酶B外肽酶活性的较低最适pH一致。从组织蛋白酶B的肽基二肽酶活性这个例子中我们得出结论，C末端延伸部分的去除可能发生在发现有活性组织蛋白酶B的任何细胞内区室中。
