Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada.
Biol Chem. 2010 Apr;391(4):381-90. doi: 10.1515/BC.2010.045.
Kallikrein-related peptidases (KLKs) are secreted serine proteinases with trypsin or chymotrypsin-like activity. Several family members, such as KLKs 6 and 10, are potential ovarian cancer biomarkers. Recently, using a newly developed assay for active KLK6, we found that only a very small proportion of immunoreactive KLK6 in tumor-derived clinical samples (malignant ascites fluid), in cerebrospinal fluid, and in cancer cell line supernatants is enzymatically active. We therefore hypothesized that a proportion of other immunoreactive KLKs in such samples could be present, but might be partly complexed to endogenous serine proteinase inhibitors. Using a combination of immunological isolation of the enzymes, activity-based probe analysis and proteomics, we identified active KLK10 in ovarian cancer ascites and we provide preliminary data that the activity of other KLKs present in these samples can be decreased by known proteinase inhibitors (e.g., alpha2-macroglobulin, alpha1-antitrypsin). Our data suggest that the enzymatic activity of ovarian cancer-released KLKs that are detected by regular immunoassays is low in vivo and very likely regulated by proteinase inhibitors.
激肽释放酶相关肽酶（KLKs）是分泌的丝氨酸蛋白酶，具有胰蛋白酶或糜蛋白酶样活性。一些家族成员，如 KLKs6 和 10，是潜在的卵巢癌生物标志物。最近，我们使用新开发的活性 KLK6 测定法发现，肿瘤来源的临床样本（恶性腹水）、脑脊液和癌细胞系上清液中的免疫反应性 KLK6 中只有很小一部分具有酶活性。因此，我们假设此类样本中其他免疫反应性 KLKs 的一部分可能存在，但可能部分与内源性丝氨酸蛋白酶抑制剂结合。我们通过酶的免疫分离、基于活性的探针分析和蛋白质组学的组合，鉴定了卵巢癌腹水中的活性 KLK10，并提供了初步数据表明，这些样本中存在的其他 KLKs 的活性可以被已知的蛋白酶抑制剂（例如，α2-巨球蛋白、α1-抗胰蛋白酶）降低。我们的数据表明，通过常规免疫测定法检测到的卵巢癌释放的 KLKs 的酶活性在体内较低，并且很可能受到蛋白酶抑制剂的调节。
