Kageyama T, Takahashi K
J Biochem. 1983 Mar;93(3):743-54. doi: 10.1093/jb/93.3.743.
Activation of porcine pepsinogen at pH 2.0 was found to proceed simultaneously by two different pathways. One pathway is the direct conversion process of pepsinogen to pepsin, releasing the intact activation segment. The isolation of the released 44-residue segment was direct evidence of this one-step process. At pH 5.5 the segment bound tightly to pepsin to form a 1:1 pepsin-activation segment complex, which was chromatographically indistinguishable from pepsinogen. The other is a stepwise-activating or sequential pathway, in which pepsinogen is activated to pepsin through intermediate forms, releasing activation peptides stepwisely. These intermediate forms were isolated and characterized. The major intermediate form was shown to be generated by removal of the amino-terminal 16 residues from pepsinogen. The released peptide mixture was composed of two major peptides comprising residues 1-16 and 17-44, and hence the stepwise-activating process was deduced to be mainly a two-step process.
发现在pH 2.0条件下猪胃蛋白酶原的激活通过两种不同途径同时进行。一种途径是胃蛋白酶原直接转化为胃蛋白酶的过程，释放完整的激活片段。释放出的44个残基片段的分离是这一步骤过程的直接证据。在pH 5.5时，该片段与胃蛋白酶紧密结合形成1:1的胃蛋白酶-激活片段复合物，其在色谱上与胃蛋白酶原无法区分。另一种是逐步激活或连续途径，其中胃蛋白酶原通过中间形式被激活为胃蛋白酶，逐步释放激活肽。这些中间形式被分离并进行了表征。主要的中间形式显示是由胃蛋白酶原去除氨基末端的16个残基产生的。释放出的肽混合物由包含残基1-16和17-44的两种主要肽组成，因此逐步激活过程被推断主要是一个两步过程。
