Carbohydrate-binding proteins of human serum: isolation of two mannose/fucose-specific lectins.
Two lectins with specificities for mannose and fucose have been isolated from human serum by affinity chromatography. One mannose-binding protein (MBP 1) has a native Mr of 700,000 with subunits of Mr 32,000 and has specificities for N-acetylglucosamine, N-acetylmannosamine and glucose as well as for mannose and fucose. The other mannose-binding protein (MBP 2) has a native Mr of 200,000 with subunits of Mr 28,000 and is specific only for mannose and fucose. MBP 2 appears to recognize the core sugars of asparagine-linked oligosaccharides as well as the terminal sugars. Both lectins are calcium-dependent, requiring approx. 0.095 mM calcium for half-maximal binding. MBP 1 binds maximally between pH 7-9, whereas MBP 2 has a pH optimum of 6-7. The binding activity of both proteins decreases rapidly below pH 5. The apparent association constants (Ka) for binding to mannon are 2.1 X 10(8) M-1 for MBP 1 and 1.3 X 10(8) M-1 for MBP 2. These data provide further evidence of the complex nature of mammalian carbohydrate recognition systems.
D000117:Acetylglucosamine / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000097:blood*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005643:Fucose / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006595:Hexosamines / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007118:Immunoassay; D008358:Mannose / Q000378:metabolism*; D037241:Mannose-Binding Lectins; D008970:Molecular Weight
D002352:Carrier Proteins; D006595:Hexosamines; D037241:Mannose-Binding Lectins; D005643:Fucose; D005947:Glucose; D008358:Mannose; D002118:Calcium; D000117:Acetylglucosamine; C002022:N-acetylmannosamine