| Autor: |
Muta, Tatsushi, Seki, Noriaki, Takaki, Yoshie, Hashimoto, Ryuji, Oda, Toshio, Iwanaga, Atsufumi, Tokunaga, Fuminori, Iwanaga, Sadaaki |
| Zdroj: |
Journal of Biological Chemistry; January 1995, Vol. 270 Issue: 2 p892-897, 6p |
| Abstrakt: |
Horseshoe crab hemocyte lysate responds to (1→3)-β-D-glucans, initiating an enzymatic cascade, which culminates in clot formation.We have purified to homogeneity the serine protease zymogen factor G, which is directly activated by (1→3)-β-D-glucans and which initiates the hemolymph clotting cascade. Factor G is a heterodimeric protein composed of two noncovalently associated subunits α (72 kDa) and β (37 kDa). In the presence of (1→3)-β-D-glucans such as curdlan and paramylon, factor G is autocatalytically activated to an active serine protease named factor G. This activation is accompanied by limited proteolysis of both subunits: the 72-kDa subunit α is cleaved to 55-kDa and 17-kDa fragments, and the 37-kDa subunit β is shortened to 34 kDa. Longer incubations with (1→3)-β-D-glucans result in cleavage of the 55-kDa fragment to 46 kDa and the 34-kDa fragment to 32 kDa, with concomitant loss of amidase activity. Reconstitution experiments using purified proteins participating in the hemolymph clotting cascade demonstrate that factor G is capable of activating proclotting enzyme directly, resulting in the conversion of coagulogen to coagulin gel. Thus, purified factor G is shown to be the primary initiator of the (1→3)-β-D-glucan-sensitive coagulation pathway in the horseshoe crab hemocyte lysate. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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