Davey J, Davis K, Imai Y, Yamamoto M, Matthews G
School of Biochemistry, University of Birmingham, UK.
EMBO J. 1994 Dec 15;13(24):5910-21. doi: 10.1002/j.1460-2075.1994.tb06936.x.
The activation of pro-hormones and many precursor proteins involves cleavage by endopeptidases belonging to the subtilisin-like family of enzymes. Here we describe the isolation and characterization of the first member of this family from the fission yeast Schizosaccharomyces pombe. The enzyme, which has been named krp for KEX2-related protease, is a type I membrane-bound endopeptidase that cleaves substrates after pairs of dibasic residues. It appears to be synthesized as a pre-pro-protein that is likely to undergo processing following translocation into the endoplasmic reticulum. Processing has been characterized in a cell-free translation/translocation system prepared from Xenopus eggs. Krp is N-glycosylated on all five of its potential sites and both the pre-sequence and the pro-sequence are quickly removed following translocation, the latter probably by autocatalytic cleavage. The inhibitor profile of krp broadly reflects the known properties of the eukaryotic subtilisin proteases, while its pH and Ca2+ dependence are consistent with it being active within the secretory pathway. One of its physiological substrates is likely to be the pheromone precursor pro-P-factor, which it is shown to process in an in vitro system, but identification of other substrates is complicated because, unlike other members of this family, krp is essential for cell viability.
激素原和许多前体蛋白的激活涉及到枯草杆菌蛋白酶样家族的内肽酶的切割作用。在此，我们描述了从裂殖酵母粟酒裂殖酵母中分离并鉴定该家族的首个成员。这种酶被命名为Krp（KEX2相关蛋白酶），是一种I型膜结合内肽酶，可在双碱性氨基酸残基对之后切割底物。它似乎以前体-前体蛋白的形式合成，在转运到内质网后可能会进行加工处理。加工过程已在由非洲爪蟾卵制备的无细胞翻译/转运系统中得到了表征。Krp在其所有五个潜在位点上都进行了N-糖基化，并且前导序列和前肽序列在转运后很快被去除，后者可能是通过自催化切割。Krp的抑制剂谱大致反映了真核枯草杆菌蛋白酶的已知特性，而其对pH和Ca2+的依赖性与其在分泌途径中的活性一致。其生理底物之一可能是信息素前体pro-P-因子，已证明它在体外系统中对其进行加工处理，但由于与该家族的其他成员不同，Krp对细胞活力至关重要，因此鉴定其他底物较为复杂。
