Schilling Klaus, Körner Alexandra, Sehmisch Saskia, Kreusch Annett, Kleint Ramona, Benedix Yvonne, Schlabrakowski Anne, Wiederanders Bernd
Institut für Biochemie I, Universitätsklinikum Jena, Nonnenplan 2, D-07743 Jena, Germany.
Biol Chem. 2009 Feb;390(2):167-74. doi: 10.1515/BC.2009.023.
Cathepsin L-like endopeptidases of the papain family are synthesized as proenzymes. N-terminal proregions are essential for folding and latency of the enzyme unit. While selectivity has been reported for the inhibitory function of papain-family propeptides, there is no systematic investigation of the selectivity of their chaperone-like function to date. The chaperone-like cross-reactivity between the cathepsins S, K, and L were thoroughly quantified in trans-experiments, i.e., with isolated propeptides and mature enzymes, and compared to the inhibitory cross-reactivity. The three endopeptidases have been chosen due to only minimal evolutionary distance and nearly identical X-ray structures of their zymogenes. The intramolecular chaperone function of the proregion was found to be more selective than the inhibitory activity and significant differences were found between the selectivity profiles, underlining the assumption that the inhibitory and the chaperone-like propeptide functions are autonomous. Considering the data published on the intramolecular chaperone-like propeptide function within other protease classes as well, our data suggest that intrinsically structured propeptides are more selective than intrinsically unstructured propeptides, i.e., those adopting tertiary structure elements only in complex with their maternal enzyme.
木瓜蛋白酶家族的组织蛋白酶L样内肽酶以酶原形式合成。N端前区对于酶单位的折叠和潜伏性至关重要。虽然已有报道木瓜蛋白酶家族前肽的抑制功能具有选择性，但迄今为止，尚未对其伴侣样功能的选择性进行系统研究。在反式实验中，即使用分离的前肽和成熟酶，对组织蛋白酶S、K和L之间的伴侣样交叉反应性进行了全面定量，并与抑制性交叉反应性进行了比较。选择这三种内肽酶是因为它们的酶原进化距离极小且X射线结构几乎相同。发现前区的分子内伴侣功能比抑制活性更具选择性，并且在选择性谱之间发现了显著差异，这突出了抑制性和伴侣样前肽功能是自主的这一假设。考虑到其他蛋白酶类别中关于分子内伴侣样前肽功能的已发表数据，我们的数据表明，内在结构化的前肽比内在非结构化的前肽更具选择性，即那些仅在与其母体酶结合时才采用三级结构元件的前肽。
