Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor

作者：Kerr Felicity K; Thomas Adele R; Wijeyewickrema Lakshmi C; Whisstock James C; Boyd Sarah E; Kaiserman Dion; Matthews Antony Y; Bird Phillip I; Thielens Nicole M; Rossi Veronique; Pike Robert N^*

来源：Molecular Immunology, 2008, 45(3): 670-677.

DOI：10.1016/j.molimm.2007.07.008

• mannose-binding lectin-associated serine protease-2
• complement
• active site specificity
• C1s
• C1-inhibitor
• serpin
• protease

Complement is a central component of host defence, but unregulated activation can contribute to disease. The system can be initiated by three pathways: classical, alternative and lectin. The classical and lectin pathways are initiated by the C1 and mannose-binding lectin (MBL) or ficolin complexes, respectively, with C1s the executioner protease of the C1 complex and MASP-2 its counterpart in the lectin complexes. These proteases in turn cleave the C4 and C2 components of the system. Here we have elucidated the cleavage specificity of MASP-2 using a randomised substrate phage display library. Apart from the crucial P, position, the MASP-2 S-2 and S-3 subsites (in that order) play the greatest role in determining specificity, with Gly residues preferred at P-2 and Leu or hydrophobic residues at P-3-Cleavage of peptide substrates representing the known physiological cleavage sequences in C2, C4 or the serpin C1-inhibitor (a likely regulator of MASP-2) revealed that MASP-2 is up to 1000 times more catalytically active than C1s. C1-inhibitor inhibited MASP-2 50-fold faster than C1s and much faster than any other protease tested to date, implying that MASP-2 is a major physiological target of C1-inhibitor.

• 出版日期2008-2