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Jens Christian Jensenius

Substrate specificities of recombinant mannan-binding lectin-associated serine proteases-1 and -2

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Mannan-binding lectin (MBL)-associated serine proteases-1 and 2 (MASP-1 and MASP-2) are homologous modular proteases that each interact with MBL, an oligomeric serum lectin involved in innate immunity. To precisely determine their substrate specificity, human MASP-1 and MASP-2, and fragments from their catalytic regions were expressed using a baculovirus/insect cells system. Recombinant MASP-2 displayed a rather wide, C1s-like esterolytic activity, and specifically cleaved complement proteins C2 and C4, with relative efficiencies 3- and 23-fold higher, respectively, than human C1s. MASP-2 also showed very weak C3 cleaving activity. Recombinant MASP-1 had a lower and more restricted esterolytic activity. It showed marginal activity toward C2 and C3, and no activity on C4. The enzymic activity of both MASP-1 and MASP-2 was specifically titrated by C1 inhibitor, and abolished at a 1:1 C1 inhibitor:protease ratio. Taken together with previous findings, these and other data strongly support the hypothesis that MASP-2 is the protease that, in association with MBL, triggers complement activation via the MBL pathway, through combined self-activation and proteolytic properties devoted to C1r and C1s in the C1 complex. In view of the very low activity of MASP-1 on C3 and C2, our data raise questions about the implication of this protease in complement activation.
Original languageEnglish
JournalJournal of Biological Chemistry
Pages (from-to)40880-7
Number of pages8
Publication statusPublished - 2001

    Research areas

  • Base Sequence, Catalysis, Complement Activation, DNA Primers, Electrophoresis, Polyacrylamide Gel, Esters, Humans, Hydrolysis, Kinetics, Mannose-Binding Protein-Associated Serine Proteases, Recombinant Proteins, Serine Endopeptidases, Serine Proteinase Inhibitors, Substrate Specificity

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