Yoon Hyesook, Laxmikanthan Gurunathan, Lee Jihun, Blaber Sachiko I, Rodriguez Aaron, Kogot Joshua M, Scarisbrick Isobel A, Blaber Michael
Department of Biomedical Sciences, Florida State University, Tallahassee, Florida 32306-4300, USA.
J Biol Chem. 2007 Nov 2;282(44):31852-64. doi: 10.1074/jbc.M705190200. Epub 2007 Sep 6.
The human kallikrein (KLK)-related peptidases are the largest family of serine peptidases, comprising 15 members (KLK1-15) and with the majority (KLK4-15) being identified only within the last decade. Members of this family are associated with important diseased states (including cancer, inflammation, and neurodegeneration) and have been utilized or proposed as clinically important biomarkers or therapeutic targets of interest. All human KLKs are synthesized as prepro-forms that are proteolytically processed to secreted pro-forms via the removal of an amino-terminal secretion signal peptide. The secreted inactive pro-KLKs are then activated extracellularly to mature peptidases by specific proteolytic release of their amino-terminal propeptide. Although a key step in the regulation of KLK function, details regarding the activation of the human pro-KLKs (i.e. the KLK "activome") are unknown, to a significant extent, but have been postulated to involve "activation cascades" with other KLKs and endopeptidases. To characterize more completely the KLK activome, we have expressed from Escherichia coli individual KLK propeptides fused to the amino terminus of a soluble carrier protein. The ability of 12 different mature KLKs to process the 15 different pro-KLK peptide sequences has been determined. Various autolytic and cross-activation relationships identified using this system have subsequently been characterized using recombinant pro-KLK proteins. The results demonstrate the potential for extensive KLK activation cascades and, when combined with available data for the tissue-specific expression of the KLK family, permit the construction of specific regulatory cascades. One such tissue-specific cascade is proposed for the central nervous system.
人激肽释放酶（KLK）相关肽酶是丝氨酸肽酶中最大的家族，由15个成员（KLK1 - 15）组成，其中大多数成员（KLK4 - 15）是在过去十年中才被鉴定出来的。该家族成员与重要疾病状态（包括癌症、炎症和神经退行性变）相关，并且已被用作或被提议作为具有临床重要性的生物标志物或感兴趣的治疗靶点。所有人类KLK均以前体形式合成，通过去除氨基末端分泌信号肽经蛋白水解加工为分泌型前体形式。分泌的无活性前体KLK随后在细胞外通过其氨基末端前肽的特异性蛋白水解释放而被激活为成熟肽酶。尽管这是KLK功能调节中的关键步骤，但在很大程度上，关于人类前体KLK激活（即KLK“激活组”）的细节尚不清楚，但据推测涉及与其他KLK和内肽酶的“激活级联反应”。为了更全面地表征KLK激活组，我们从大肠杆菌中表达了与可溶性载体蛋白氨基末端融合的单个KLK前肽。已经确定了12种不同成熟KLK处理15种不同前体KLK肽序列的能力。随后使用重组前体KLK蛋白对使用该系统鉴定的各种自溶和交叉激活关系进行了表征。结果证明了广泛的KLK激活级联反应的可能性，并且当与KLK家族组织特异性表达的现有数据相结合时，允许构建特定的调节级联反应。本文提出了一种针对中枢神经系统的此类组织特异性级联反应。
