Some Fibrinogenolytic Properties Of Lamphredin Secreted By Buccal Glands Of Lampetra Japonica

The buccal gland secretion (lamphredin) of Lampetra japonica, which is one of the ancient cyclostomota representative animals, has been known to act in anticoagulation. The secretion exhibits mainly two protein bands by native-PAGE and SDS-PAGE, namely buccal gland secretion protein-1 (BGSP-1, 140,000 Da) and buccal gland secretion protein-2 (BGSP-2, 27,500 Da). The N-terminal 20 amino acids of BGSP-1 (EAESF QNLKT RICGG LNGLG) and BGSP-2 (TSVND WKLLD TKLSA NRKVI) were sequenced. BGSP-1, BGSP-2 and some small peptides were isolated from the buccal gland secretion by a Sephadex G-75 column, but only BGSP-1 showed the fibrinogenolytic activity. Lamphredin or BGSP-1 rapidly degraded the alpha chain of human fibrinogen, and more slowly the beta chain and hardly the gamma chain. The degradation fragments of fibrinogen exhibited a similar map of BGSP-1 to lamphredin on SDS-PAGE, by cleavage at Ala₁₀-Glu₁₁ and His₃₆₈-Ser₃₆₉ of f ibrinogen. BGSP-1 was also observed to hydrolyze neuronal tau protein at Glu₁₂-Asp₁₃ and Gln₂₄₄-Thr₂₄₅. Under the same conditions, hydrolysis of BSA and hemoglobin could not be observed in the presence of lamphredin. Further study showed that lamphredin and BGSP-1 were inactivated in the presence of a metal chelating agent EDTA-2Na. However, addition of Ca²⁺ or Mg²⁺ except Zn²⁺ restored their fibrinogenolytic activity. This suggests that BGSP-1 is a metal-activated proteinase with a broad substrate specificity in the buccal gland. Furthermore, the secretion showed cytolytic property during the cell culture of SH-SY5Y and human HeLa cell lines, and fifty time-diluted lamphredin can markedly induce cell death, suggesting that lamphredin is helpful to lamprey on feeding its hosts.