Proteolytic activities of two types of mannose-binding lectin-associated serine protease.
Mannose (or mannan)-binding lectin (MBL) is an oligomeric serum lectin that plays a role in innate immunity by activating the complement system. In human, two types of MBL-associated serine protease (MASP-1 and MASP-2) and a truncated protein of MASP-2 (small MBL-associated protein; sMAP or MAp19) are complexed with MBL. To clarify the proteolytic activities of MASP-1 and MASP-2 against C4, C2, and C3, we isolated these two types of MASP in activated forms from human serum by sequential affinity chromatography. On an anti-MASP-1 column, MASP-2 passed through the column in the presence of EDTA and high salt concentration, whereas MASP-1 was retained. Isolated MASP-1 and MASP-2 exhibited proteolytic activities against C3 and C4, respectively. C2 was activated by both MASPs. C1 inhibitor (C1 INH), an inhibitor for C1r and C1s, formed equimolar complexes with MASP-1 and MASP-2 and inhibited their proteolytic activities.
Matsushita
M
M
Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima, Japan. mmatsu@fmu.ac.jp
Thiel
S
S
Jensenius
J C
JC
Terai
I
I
Fujita
T
T
D001667:Binding, Competitive / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism*; D037222:Collectins; D003167:Complement Activation / Q000276:immunology; D003174:Complement C1 Inactivator Proteins / Q000378:metabolism; D004306:Dose-Response Relationship, Immunologic; D004789:Enzyme Activation / Q000276:immunology; D006801:Humans; D006868:Hydrolysis; D037102:Lectins / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism*; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000378:metabolism
D002352:Carrier Proteins; D037222:Collectins; D003174:Complement C1 Inactivator Proteins; D037102:Lectins; D015842:Serine Proteinase Inhibitors; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases; D008358:Mannose