Primary Structure of a Coagulant Enzyme, Bilineobin, from Agkistrodon bilineatus Venom

The amino acid sequence and disulfide bridge location of the coagulant enzyme, named bilineobin, isolated from the venom of Agkistrodon bilineatus was determined by Edman sequencing of the peptides derived from digests with cyanogen bromide, clostripain, Staphylococcus aureus V8 protease, trypsin, and chymotrypsin. This enzyme has a molecular weight of 57,000 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; however, bilineobin consists of 235 amino acids and has a calculated molecular weight of 26,481, The enzyme contains fucose, GlcNAc, galactose, mannose and NeuAc and six N-linked glycosylation consensus sites. The carboxyterminal amino acid, proline, was determined using carboxypeptidase Y. The six disulfide bonds of bilineobin link Cys78 to Cys234, Cys120 to Cys188, Cys178 to Cys203, Cys7 to Cys141, Cys152 to Cys167, and Cys28 to Cys44. The amino acid sequence similarity to flavoxobin (T. C. Shieh et al., 1988, J. Biochem (Tokyo) 103, 596-605) and batroxobin (N. Itoh et al., 1987, J. Biol. Chem. 262, 3132-3135) was 67%, The deglycosylated enzyme more rapidly generated fibrinopeptide A than native bilineobin.