Primary structure of a thrombin-like serine protease, kangshuanmei, from the venom of Agkistrodon halys brevicaudus stejneger

The complete amino acid sequence of the thrombin-like serine protease, named kangshuanmei, isolated from the venom of a Chinese snake Agkistrodon halys brevicaudus stejneger, was determined by Edman degradation. The serine protease was composed of 236 amino acid residues and conserved the catalytic triad as His43, Asp88 and Ser182. The protease had four sites of asparagine-linked glycosylation at 81, 99, 148 and 229, and contained fucose, N-acetylglucosamin, galactose, mannose and N-acetylneuraminic acid. The amino acid sequence exhibited considerable similarities with other thrombin-like proteases isolated from the snake venoms of the Viperidae family. However, the enzymatic characteristics of kangshuanmei distinct from that of thrombin and the other protease from the venom of Viperidae family may be derived from the structural difference of the sequence in the functional regions, especially corresponding to thrombin exosite 1, 2 and hydrophobic pocket.