A new type of lectin discovered in a fish, flathead (Platycephalus indicus), suggests an alternative functional role for mammalian plasma kallikrein(*)

作者：Tsutsui Shigeyuki^*; Okamoto Masaki; Ono Miyuki; Suetake Hiroaki; Kikuchi Kiyoshi; Nakamura Osamu; Suzuki Yuzuru; Watanabe Tasuku

来源：Glycobiology, 2011, 21(12): 1580-1587.

DOI：10.1093/glycob/cwr070

• coagulation factor XI
• lectin
• plasma kallikrein
• skin mucus

A skin mucus lectin exhibiting a homodimeric structure and an S-S bond between subunits of similar to 40 kDa was purified from flathead Platycephalus indicus (Scorpaeniformes). This lectin, named FHL (FlatHead Lectin), exhibited mannose-specific activity in a Ca2+-dependent manner. Although FHL showed no homology to any previously reported lectins, it did exhibit similar to 20% identity to previously discovered plasma kallikreins and coagulation factor XIs of mammals and Xenopus laevis. These known proteins are serine proteases and play pivotal roles in the kinin-generating system or the blood coagulation pathway. However, alignment analysis revealed that while FHL lacked a serine protease domain, it was homologous to the heavy-chain domain of plasma kallikreins and coagulation factor XI therefore suggesting that FHL is not an enzyme but rather a novel animal lectin. On the basis of this finding, we investigated the lectin activity of human plasma kallikrein and revealed that it could indeed act as a lectin. Other genes homologous to FHL were also found in the genome databases of some fish species, but not in mammals. In contrast, plasma kallikreins and coagulation factor XI have yet to be identified in fish. The present findings suggest that these mammalian enzymes may have originally emerged as a lectin and may have evolved into molecules with protease activity after separation from common ancestors.

• 出版日期2011-12